Final Capsule – Civil Engineering (ACiE)

NEC License Preparation • 600 High-Yield One-Liners

All 600 points are listed below, numbered 1 to 600 — just scroll and read

Part 1: Construction Materials & Their Tests 1–4040 points

Cement is manufactured by burning an intimate mixture of calcareous (limestone) and argillaceous (clay) materials at about 1400–1500 °C in a rotary kiln to form clinker, which is then ground with 2–3% gypsum.
The four main compounds of OPC are C3S (alite), C2S (belite), C3A and C4AF; C3S gives early strength (about 7-day strength) and C2S gives later (28-day and beyond) strength with less heat.
C3A is responsible for the flash set of cement; gypsum added at the grinding stage controls the rate of hydration of C3A.
Minimum compressive strength: OPC 33 grade – 16 MPa at 7 days and 33 MPa at 28 days (IS 269); 43 grade – 23 MPa / 43 MPa (IS 8112); 53 grade – 27 MPa / 53 MPa (IS 12269).
Fineness of cement is measured by Blaine's air permeability apparatus; the minimum specific surface of OPC is 225 m²/kg.
The standard (normal) consistency of OPC is about 30–35% of water by weight of cement and is determined with the Vicat apparatus.
Setting time of OPC: initial setting time not less than 30 minutes and final setting time not more than 600 minutes (10 hours).
Soundness of cement is tested by the Le Chatelier method (un-boiled) and the autoclave method; the permissible Le Chatelier expansion for OPC is 10 mm maximum.
Heat of hydration order: C3A > C3S > C4AF > C2S. Low-heat cement is made by reducing the C3A and C3S content and is used in mass concrete (dams).
Sulphate-resisting cement has C3A limited to 5% maximum; it is used for canal lining, marine works, chimney and foundations in sulphate-bearing soils.
In quick-setting cement a small amount of aluminium sulphate is added in place of gypsum; the initial setting time is about 5 minutes and the final setting time about 30 minutes.
Pozzolana (fly ash, surkhi, volcanic ash) reacts with the free lime liberated during hydration to form additional cementitious compounds, reducing heat of hydration and increasing impermeability.
Rapid-hardening cement (IS 8041) has a higher C3S and C3A content and attains about 16 MPa in 3 days, which is roughly equal to the 7-day strength of OPC; it is used for road repairs and early formwork removal.
Abrams' water-cement law: for given materials and full compaction, the strength of concrete depends only on the water-cement ratio and is inversely proportional to it.
The standard modular brick size is 190 × 90 × 90 mm; with a 10 mm mortar joint it occupies 200 × 100 × 100 mm (1 m³ holds 500 bricks).
First-class brick: compressive strength not less than 10.5 MPa and water absorption not more than 20% by weight after 24 hours of immersion.
Second-class brick: strength not less than 7 MPa and absorption up to 22%; third-class brick: strength not less than 3.5 MPa and absorption up to 25%.
Efflorescence test: a brick immersed in water for 24 hours and then allowed to dry should show no grey or white deposits; white patches indicate the presence of soluble salts.
A good brick gives a clear metallic ringing sound when struck with another brick and its broken surface should be bright, homogeneous and free from lumps.
A brick dropped from a height of about 1 m on a hard surface should not break; this is the standard field test for toughness.
Bulking of sand: 4–5% moisture by weight causes bulking of about 20–40%; bulking is maximum at about 5–6% moisture content and decreases with further addition of water.
Fine aggregate passes the 4.75 mm IS sieve and coarse aggregate is retained on it; the fineness modulus of fine sand is 2.2–2.6, medium sand 2.6–2.9 and coarse sand 2.9–3.2.
Road aggregates: impact value not more than 30% for the wearing course and 35% for the base course; crushing value not more than 30% for the surface course; Los Angeles abrasion value not more than 40% for the wearing course.
Flakiness index of road aggregate should not exceed 35% and the elongation index 15%; both are undesirable because they reduce workability and strength.
Seasoning of timber reduces the moisture content to about 10–12% for building use, increases strength, reduces shrinkage and makes the timber suitable for painting and preservative treatment.
Fat (rich) lime contains about 95% CaO and slakes vigorously; hydraulic lime contains 5–30% clay and sets under water; poor (lean) lime contains more than 30% clay.
Mild steel (Fe 250) has a yield stress of 250 MPa; HYSD bars are Fe 415 and Fe 500 (IS 1786); deformed (ribbed) bars give about 60% higher bond strength than plain bars.
Granite and basalt are igneous, sandstone and limestone are sedimentary, and marble and slate are metamorphic rocks; a good building stone has a specific gravity of 2.4–2.8 and water absorption less than 5%.
Smith's test: a piece of stone immersed in water for 24 hours – clear water indicates the absence of earthy matter; crushing strength of a good building stone should exceed 100 MPa.
In paint, the pigment (white lead, zinc oxide, red lead) gives colour and opacity, the vehicle (linseed oil) carries the pigment, and driers (litharge, red lead) accelerate drying; distemper is used for interior walls.
Nominal mixes (IS 456): M7.5 = 1:4:8, M10 = 1:3:6, M15 = 1:2:4, M20 = 1:1.5:3, M25 = 1:1:2 (cement : sand : coarse aggregate by volume).
Workability is measured by the slump test, compaction factor and Vee-Bee test; slump 0–25 mm is very low, 25–75 mm medium and above 75 mm high workability.
Compaction factor: about 0.78 for very low, 0.85 for low, 0.92 for medium and 0.95 for high workability; the slump for pumped concrete is 100–150 mm.
The 150 mm cube is the standard specimen in India/Nepal; the cylinder (150 × 300 mm) strength is about 0.8 times the cube strength.
Modulus of elasticity of concrete (short term, static) Ec = 5000 √fck N/mm² as per IS 456.
Curing: minimum 7 days for OPC concrete and at least 10 days when mineral admixtures or blended cement are used; curing stops at the surface when the concrete dries below the critical humidity.
Bleeding is a form of segregation in which water rises to the surface of freshly placed concrete; it increases with a high water-cement ratio, lean mixes and over-vibration.
Admixtures: accelerators (calcium chloride), retarders (gypsum, sugar), plasticisers (lignosulphonates), superplasticisers, air-entraining agents and pozzolanic admixtures.
Non-destructive tests on hardened concrete: rebound hammer (surface hardness and strength index), ultrasonic pulse velocity (quality and homogeneity) and core cutting (actual strength).
UPV interpretation: above 4.5 km/s excellent, 3.5–4.5 km/s good, 3.0–3.5 km/s medium (doubtful) and below 3.0 km/s poor quality concrete.

Part 2: Building Construction, Masonry & Carpentry 41–6020 points

English bond consists of alternate courses of headers and stretchers and is the strongest bond; Flemish bond has alternate headers and stretchers in the same course and gives better appearance.
A queen closer is placed next to the quoin header to develop the face lap; a bat is a piece of brick cut across its width and a bevelled closer has one end cut at an angle.
Masonry should be raised in lifts not exceeding 1.5 m in a day so that the lower mortar is not squeezed out by the fresh load.
The frog (depression) of a brick is kept facing upwards so that it is filled with mortar and forms a key; a header shows the frog more completely than a stretcher.
In stone masonry, through stones (bond stones) are provided at about 1.5–2 m intervals, and the beds of the stones should be perpendicular to the direction of the pressure.
Coursed rubble masonry of the first class uses hammer-dressed stones in courses of equal height with through stones; random rubble masonry is used for foundations and rough work.
A plinth is the portion of the structure between the natural ground level and the floor level; the plinth height is generally kept 300–600 mm above the ground to protect against splash and flooding.
A damp-proof course (DPC) is provided at plinth level to prevent rising dampness; a 40 mm thick PCC 1:2:4 course with waterproofing compound is the usual provision.
Excavation for footings: the bottom width of the trench is taken as the footing width plus about 150 mm working space on each side.
A brick nogging partition is about 8–10 cm (half-brick) thick and is used only as a non-load-bearing partition; studs are of timber with brick masonry in between.
Minimum thickness of a load-bearing wall is 200 mm for a single storey and 300 mm for two storeys; the slenderness ratio of a load-bearing wall should not exceed 27 (IS 1905).
The bearing of a lintel on each side of the opening should be at least 100 mm (preferably 150 mm); a relieving arch is constructed above a lintel to transfer the load.
Arches carry load mainly in compression and the horizontal thrust is resisted by abutments; types are segmental, semicircular, pointed (Gothic), jack (flat) and relieving.
In corbelling, the projection of each brick course should not exceed one-quarter of its length (about 60 mm maximum per course) to avoid overturning.
Roof types: lean-to, gable, hip, gambrel, mansard and saw-tooth (north-light for factories); a Madras terrace or RCC slab is used for flat roofs.
In a door shutter the vertical members are called stiles and the horizontal members rails; the outer frame is called the door frame and the vertical side member of the frame is the jamb.
Windows: sash window (vertical sliding), casement window (hinged at the side), louvred window (ventilation), lantern (light over a large room) and clerestory window.
Staircase rules: riser 150–190 mm, tread 250–300 mm, 2R + T = 550–650 mm (Blondel's rule), headroom not less than 2.1 m, number of risers in a flight 3 to 12, and the landing width equal to the width of the flight.
Damp-proofing methods: DPC membrane, cavity wall construction, surface treatment (cement plaster with waterproofing), drainage of ground water and electro-osmosis.
Building by-laws control the line of the building, setbacks, floor-area ratio (FAR), ground coverage, height, open spaces, ventilation and fire safety; in Nepal these are enforced through the municipal building by-laws and the National Building Code.

Part 3: Geometric Properties of Sections 61–7212 points

Centroid of a triangle is at h/3 from the base; of a semicircle at 4R/(3π) = 0.424R from the diameter; of a quarter circle at 0.424R from each of the straight edges.
Moment of inertia about the centroidal axis: rectangle bd³/12, triangle bd³/36, circle πd⁴/64; for a semicircle it is πd⁴/128 about the base (diameter) axis and 0.00686 d⁴ about the centroidal axis.
Section modulus Z = I/y: rectangle bd²/6, circle πd³/32, hollow circular section π(D⁴ − d⁴)/(32D), triangle bd²/24 measured from the centroid.
Radius of gyration k = √(I/A); for a rectangle about the centroidal axis parallel to the base, k = d/√12 = 0.289d.
Parallel axis theorem: I = I_G + Ah². Perpendicular axis theorem (plane lamina only): Iz = Ix + Iy.
Polar moment of inertia of a solid circle J = πd⁴/32 = Ix + Iy; for a hollow shaft J = π(D⁴ − d⁴)/32.
In an I-section the flanges resist almost the whole bending moment (material far from the neutral axis) while the web carries about 90–95% of the shear force.
A principal axis is an axis about which the product of inertia is zero; every axis of symmetry is a principal axis.
For a circular section, all centroidal axes are principal axes because the moment of inertia is the same about every axis.
The elastic section modulus governs the moment at which the extreme fibre just reaches yield: My = Z · fy.
Shape factor Zp/Ze: rectangle 1.5, circle 1.7, triangle 2.34, diamond 2.0 and rolled I-section about 1.12–1.15.
For a rectangular section the plastic neutral axis coincides with the equal-area axis and the plastic modulus Zp = bd²/4.

Part 4: Surveying & Levelling 73–9927 points

The two fundamental principles of surveying are: (i) to work from whole to part, and (ii) to locate a new point by at least two measurements (linear or angular) from fixed reference points.
Chain surveying (linear surveying) is suitable for small, open, fairly level areas where only linear measurements are required and the framework of triangles can be formed.
Metric chains are 20 m (100 links of 20 cm) or 30 m long; Gunter's chain is 22 yards (66 ft, 100 links) so that 10 square chains = 1 acre; the engineer's chain is 100 ft long.
Conversions: 1 acre = 43,560 sq ft = 4047 m²; 1 hectare = 10,000 m² = 2.471 acres; 1 sq chain = 1/10 acre.
Ranging is direct when the end stations are intervisible and indirect (reciprocal ranging) when they are not; offsets are perpendicular or oblique, and offsets up to 15 m are called short offsets.
Errors that always have the same sign and accumulate are cumulative errors; those that occur sometimes positive and sometimes negative and partly cancel are compensating errors.
The corrections for slope and sag are always negative (subtractive); the correction for pull is positive; the corrections for temperature and standardisation may be positive or negative.
Correction for slope = L(1 − cos θ) = h²/(2L) approximately, and is always subtracted from the measured sloped length.
Correction for sag = W²L/(24P²) (negative), where W is the weight of the chain per span, L the span length and P the applied pull.
Reciprocal levelling is used across a river, pond or deep valley where the level cannot be set up midway; it eliminates the combined error of curvature, refraction and collimation and gives the true difference of level.
Fly levelling connects a bench mark to the working site, check levelling verifies the work, profile (longitudinal) levelling gives the section of a road or canal, and cross-sectioning gives transverse profiles.
Curvature correction = 0.0078 D² m (negative), refraction correction = 0.0011 D² m (positive) and the combined correction = 0.0067 D² m (negative), where D is the distance in km.
The sensitivity of a bubble tube increases with a larger radius of the tube, a larger diameter of the tube and a lower viscosity of the liquid, and decreases with a longer bubble and a higher temperature.
Height of Instrument method: HI = RL of BM + back sight, and RL of any point = HI − fore sight (or intermediate sight); it involves fewer arithmetic checks but is faster than the rise-and-fall method.
The rise-and-fall method provides a complete check on all the points (BS − FS = rise − fall = last RL − first RL) and is preferred for important work such as fly levelling.
Bench marks: GTS bench mark (established by the national survey department), permanent bench mark, temporary bench mark and arbitrary bench mark.
In a dumpy level the bubble tube is permanently fixed to the telescope; in a tilting level the bubble is centred immediately before each reading, which makes it more accurate for precise work.
Temporary adjustments of a theodolite are centring, levelling and elimination of parallax; permanent adjustments are the plate level, cross-hair, line of collimation, horizontal axis and altitude bubble adjustments.
Observations on both faces (face left and face right) eliminate the error of collimation, the error of the horizontal axis and the index error of the vertical circle, but not the centring error or the error of non-adjustment of the plate level.
Latitude = L cos θ and departure = L sin θ; for a closed traverse Σ latitude = 0 and Σ departure = 0; closing error = √((ΣL)² + (ΣD)²) and the permissible relative precision is 1/1000 to 1/3000 for a theodolite traverse.
Bowditch (compass) rule distributes the correction in proportion to the length of the side and is used when linear and angular measurements are equally precise; the transit rule is used when angular measurements are more precise.
Local attraction exists when the fore bearing and back bearing of a line do not differ by exactly 180°; magnetic declination is the horizontal angle between the magnetic and true meridians, and the dip is 90° at the poles and 0° at the equator.
Whole circle bearing is measured clockwise from north over 0°–360°; reduced (quadrantal) bearing is measured from the nearest north or south and lies between 0° and 90°.
Tacheometric distance D = kS cos²θ + C cos θ for an inclined sight, where the multiplying constant k = f/i is normally 100; an anallatic lens makes the additive constant C equal to zero.
The contour interval depends on the scale of the map, the purpose of the survey, the nature of the ground and the time and money available; the contour interval is inversely proportional to the scale of the map.
Contour lines never cross each other except at an overhanging cliff or a cave; around a ridge they form U- or V-shaped curves with the convexity towards the lower ground, and around a valley with the convexity towards the higher ground.
Plane table methods are radiation, intersection (triangulation), traversing and resection (two-point and three-point problems); it is quick and economical for filling in details in open country but is unsuitable in wet weather and for accurate work.

Part 5: High-Yield Mixed Capsule: Drawing, Estimating, Economics, Contracts & Project Management 100–17071 points

Standard drawing sheet sizes (IS 11664/ISO): A0 = 1189 × 840 mm, A1 = 841 × 594 mm, A2 = 594 × 420 mm, A3 = 420 × 297 mm, A4 = 297 × 210 mm.
Trimming margins are 20 mm for A0 and A1 sheets and 10 mm for A2, A3 and A4 sheets; the border is drawn inside the trimming margin.
The title block is placed in the bottom right-hand corner of the drawing sheet and its recommended size is 185 × 65 mm; it contains the title, drawing number, scale, sheet size, projection symbol and the names of the draughtsman and checker.
Line conventions: continuous thick for visible edges, continuous thin for dimension, extension and hatching lines, dashed for hidden edges, thin chain for centre lines, chain thick at the ends for cutting planes and a zigzag line for a long break.
The aligned system of dimensioning allows dimensions to be read from the bottom or the right-hand edge and is used for large drawings; the unidirectional system allows reading only from the bottom and is faster for small sheets.
Dimension lines are drawn about 8–10 mm away from the object outline and extension lines should project about 2 mm beyond the dimension line; dimension lines should not cross each other wherever possible.
Representative fraction (RF) = length on the drawing / actual length; a scale of 1 cm = 1 m gives RF = 1/100.
A plain scale reads two consecutive units (metre and decimetre) and a diagonal scale reads three consecutive units (metre, decimetre and centimetre).
Conic sections by eccentricity e: e = 0 circle, 0 < e < 1 ellipse, e = 1 parabola and e > 1 hyperbola; a conic is also the locus of a point whose ratio of distance from the focus to the directrix equals e.
Symbol R represent in dimension is Radius.
In critical path method, the relationship between total float (TF) and Free float (FF) is TF > FF. Strictly, TF ≥ FF – free float can never exceed total float; they are equal when the activity has no interfering float.
French curve is used to draw smooth free from curve.
The Bid Validity Period for bid having estimated cost up to 100 million is 90 days. Above NPR 100 million the bid validity is 120 days (PPR 2064, Rule 54); it is counted from the last date of bid submission.
Bias towards political parties is not considered a professional quality of an engineer. A professional engineer must hold the safety, health and welfare of the public paramount and act without favouritism or prejudice.
Pencil B is used to draw visual Line. H or 2H pencils are used for guidelines and construction lines, B/HB for visible (object) lines and 2B for dark visible lines.
In a company with multiple alternatives, if the company can choose only one option among them, the alternatives are mutually exclusive. If more than one alternative can be accepted at the same time they are independent alternatives.
In rate analysis, the cost of tool and equipment is taken as 3% of cost unskilled labor. In the standard rate analysis of Nepal (DoLI norms), Tools & Plants (T&P) is taken as 3% of the unskilled labour cost.
Dummy is used for grammatical purpose and logical Purpose. A dummy activity consumes neither time nor resources; it maintains the logical relationship between activities and gives each activity a unique pair of event numbers.
The isometric scale factor is cos 35°16' = 0.816; isometric projection is drawn with the isometric scale whereas isometric drawing (view) is drawn to full scale.
In first-angle projection (used in Nepal and India) the top view is placed below the front view; in third-angle projection the top view is placed above it; the symbol of projection is marked in the title block.
The minimum number of views required to describe a cylinder fully is two, and for a sphere one view with the diameter dimension is sufficient.
Types of section: full section, half section (for symmetrical objects), revolved section, removed section, broken-out section and auxiliary section.
A cutting plane line is drawn as a thin chain line with thick ends and arrows indicating the direction of sight; it is labelled with letters (A-A, B-B).
Section lining (hatching) is drawn at 45° to the horizontal with thin, equally spaced lines 1–3 mm apart; adjacent parts are hatched in opposite directions to distinguish them.
An involute is the locus of the free end of a string unwound from a circle while keeping the string taut; involute profiles are used for gear teeth with a standard pressure angle of 20°.
A cycloid is the locus of a point on the circumference of a circle rolling on a straight line; rolling outside a circle gives an epicycloid and inside gives a hypocycloid; a hypocycloid generated by a circle of half the diameter of the fixed circle is a straight line.
A helix is the locus of a point moving uniformly along the axis of a cylinder while rotating uniformly about it; lead = pitch × number of starts, and the helix angle is measured from the axis.
In an Archimedean spiral the radius vector increases uniformly with the angle of rotation; it is used for cam profiles, spiral chucks and scroll plates.
A trochoid is the locus of a point inside (inferior trochoid) or outside (superior trochoid) a circle rolling along a straight line; if the point is on the circumference the curve is a cycloid.
Development of surfaces: parallel line method for prisms and cylinders, radial line method for pyramids and cones, triangulation for transition pieces and the zone method for a sphere or ellipsoid.
For two cylinders of equal diameter whose axes intersect at right angles, the curve of intersection appears as straight lines in the view in which both axes are seen in their true length.
Types of estimates: approximate (rough cost) estimate, detailed estimate, quantity estimate, revised estimate (prepared when the sanctioned cost is likely to be exceeded by 5% or more), supplementary estimate (for additional works) and annual repair and maintenance estimate.
Approximate estimating methods: plinth area method (most common), cubic content method (most accurate), service unit method (per bed, per student, per seat) and typical bay method.
Detailed estimating methods: the long wall–short wall method (simple and easy to follow) and the centre line method (quicker and more accurate for symmetrical plans).
In the centre line method, for every junction where a wall meets another wall, half the thickness of that wall is deducted from the total centre line length.
Earthwork of a road or canal is computed by the mid-section method, the trapezoidal method or the prismoidal formula V = (L/6)(A1 + 4Am + A2); the prismoidal formula gives the most accurate result.
Area by the trapezoidal rule = d[(½)(y1 + yn) + y2 + y3 + … + yn−1]; by Simpson's one-third rule = (d/3)[(y1 + yn) + 4(y2 + y4 + …) + 2(y3 + y5 + …)], which requires an even number of divisions.
In earthwork, the horizontal distance a soil is carried is the lead and the vertical distance is the lift; lead is normally allowed free up to 30 m and lift up to 1.5 m.
Standard units of measurement: brickwork, stonework, concrete and excavation in m³; plastering, pointing, painting, formwork and damp-proof course in m²; reinforcement and steel work in kg (or tonnes); and doors/windows in numbers.
In valuation, year's purchase = 100/(rate of return + rate of sinking fund) and capitalised value = net annual income × year's purchase; obsolescence is the loss of value due to changes in style, requirements or surroundings.
Depreciation methods: straight line, declining (written down) balance, sinking fund and sum-of-years'-digits; the sinking fund factor S = i/[(1 + i)ⁿ − 1].
Time value of money: a rupee today is worth more than a rupee tomorrow; F = P(1 + i)ⁿ and P = F/(1 + i)ⁿ, where i is the interest (discount) rate per period.
The effective annual rate = (1 + r/m)^m − 1, where r is the nominal annual rate compounded m times a year; the effective rate is always greater than the nominal rate when m > 1.
Net Present Value NPV = Σ[CFt/(1 + i)^t] − initial investment; a project is economically acceptable if NPV ≥ 0 at the MARR, and among mutually exclusive alternatives the one with the highest NPV is chosen.
The Internal Rate of Return (IRR) is the discount rate that makes NPV = 0; accept the project if IRR > MARR. For mutually exclusive alternatives, incremental analysis must be used, not a simple comparison of IRRs.
The payback period is the time needed to recover the initial investment; the discounted payback period accounts for the time value of money. Both ignore cash flows after the payback point and hence ignore profitability.
Benefit-Cost Ratio BCR = present worth of benefits / present worth of costs; a project is justified when BCR ≥ 1 (used mainly for public sector projects).
Straight-line depreciation = (initial cost − salvage value)/useful life; the declining balance method applies a constant percentage to the book value and gives a higher depreciation in the early years.
Uniform series factors: present worth P = A[((1 + i)ⁿ − 1)/(i(1 + i)ⁿ)] and capital recovery A = P[i(1 + i)ⁿ/((1 + i)ⁿ − 1)].
For a bid with an estimated cost above NPR 100 million the bid validity period is 120 days; the bid security remains valid for 30 days beyond the bid validity period.
Types of contract: lump sum, unit (item) rate, cost plus percentage, cost plus fixed fee, target cost, percentage rate and turnkey; the item rate contract is the most common for road and building works in Nepal.
In Nepal the bid security is normally 2–3% of the estimated cost and the performance security is 5% of the contract price; both are submitted as bank guarantees.
Methods of procurement: open (national/international) competitive bidding, limited/sheltered bidding, sealed quotation (for small works, generally up to NPR 2 million) and direct (spot) procurement for very small values; e-bidding is compulsory above NPR 20 million for works and goods.
The defects liability (maintenance) period is generally 12 months from the date of completion; retention money of about 5% of each running bill is retained and released after the expiry of that period.
A professional engineer should hold public safety, health and welfare paramount, act as a faithful agent of the employer, disclose conflicts of interest, work only within his or her competence, avoid bribery, and sign and seal only documents he or she has prepared or supervised.
A site plan shows the plot, the north line, approaches, boundaries, setbacks and adjoining roads; a floor plan is a horizontal section cut about 1.2 m above the floor level.
An elevation shows the external appearance of a building; a section shows internal details, floor-to-floor heights, foundation depth and materials of construction.
Schedules in a working drawing list doors, windows, finishes, reinforcement and fittings; a legend explains the symbols, abbreviations and line conventions used.
The locus traced by a point moving along a pendulum from one end to another, when the pendulum oscillates, is a spiral.
In a building plan, doors and windows are shown by reference marks keyed to a schedule; the size of a door is written as width × height (for example 900 × 2100 mm).
In free-hand sketching the pencil is held at about 30–45°, long lines are drawn with arm movement rather than wrist movement, and proportions are fixed by light construction marks before darkening.
A bar chart (Gantt chart) is simple and easy to prepare but does not show the interdependence of activities, cannot show the effect of a delay on the completion date and cannot identify the critical path.
CPM is a deterministic technique based on a single time estimate for each activity and is oriented towards activities and the cost-time trade-off; PERT is a probabilistic technique based on three time estimates and is oriented towards events.
PERT expected time te = (to + 4tm + tp)/6; variance of an activity = ((tp − to)/6)² and the standard deviation of the path = √(Σ variances).
The critical path is the longest path through the network in terms of time, has zero total float and determines the earliest completion time of the project.
Total float = LS − ES = LF − EF; free float is the part of the total float that can be used without affecting the float of succeeding activities; independent float is that part which can be used without affecting either the preceding or the succeeding activities.
Crashing is the reduction of the project duration at additional cost; the cost slope = (crash cost − normal cost)/(normal duration − crash duration) and the critical activity with the least cost slope is crashed first.
The optimum project duration corresponds to the minimum total cost, which is the sum of the direct cost (increasing with time reduction) and the indirect cost (decreasing with time reduction).
Rules of a network: no looping, no dangling activities, only one start event and one end event, and no two activities may have the same pair of start and end events.
A dummy activity is shown by a dashed arrow, consumes neither time nor resources, and is used to maintain the logical relationship and the identity of activities.
Resource levelling redistributes activities within their available floats to obtain a uniform demand for resources (the project duration may increase if resources are limited); resource smoothing keeps the duration fixed and adjusts the demand within the available float.

Part 6: Soil Mechanics & Foundation Engineering 171–21545 points

Soil is a three-phase system (solid, water, air). Void ratio e = Vv/Vs, porosity n = Vv/V = e/(1 + e), air content ac = Va/Vv and degree of saturation S = Vw/Vv.
Water content w = Ww/Ws; for a fully saturated soil e = wG (S = 1), which is the fundamental relation connecting the phase quantities.
γd = γ/(1 + w) = Gγw/(1 + e); γsat = (G + e)γw/(1 + e); γ' (submerged) = (G − 1)γw/(1 + e) = γsat − γw.
Atterberg limits: liquid limit (LL), plastic limit (PL) and shrinkage limit (SL); plasticity index PI = LL − PL, liquidity index LI = (w − PL)/PI and consistency index CI = (LL − w)/PI.
The liquid limit is determined by Casagrande's apparatus (25 blows), the plastic limit by the 3 mm thread-rolling method and the shrinkage limit by oven drying a saturated soil pat (mercury displacement method).
The A-line of the plasticity chart (PI = 0.73(LL − 20)) separates clays (above the line) from silts and organic soils (below it); the toughness index = PL/flow index.
USCS/IS group symbols: GW well-graded gravel, GP poorly graded gravel, SW well-graded sand, SP poorly graded sand, ML low-plasticity silt, CL low-plasticity clay, CH high-plasticity clay, OL/OH organic soil, Pt peat.
Specific gravity of soil solids: sand 2.65–2.68, clay 2.65–2.80 and organic soils below 2.0; it is determined in the laboratory by the pycnometer (density bottle) method.
Sieve analysis is used for coarse-grained soils (particles retained on the 0.075 mm sieve) and hydrometer (sedimentation) analysis, based on Stokes' law, for fine-grained soils; Stokes' law is valid for particles between 0.2 mm and 0.02 mm.
Coefficient of uniformity Cu = D60/D10 and coefficient of curvature Cc = D30²/(D60 × D10); well-graded sand has Cu > 6 and Cc between 1 and 3, well-graded gravel Cu > 4 and Cc between 1 and 3.
Relative density Dr = (emax − e)/(emax − emin) and applies only to cohesionless soils: Dr < 35% loose, 35–65% medium dense and > 65% dense.
Darcy's law v = ki holds for laminar flow; the order of permeability is gravel 1 cm/s, sand 10¹ to 10³ cm/s, silt 10³ to 10&sup5; cm/s and clay less than 10&sup7; cm/s.
Laboratory permeability tests: constant head (coarse-grained soils) and falling head (fine-grained soils); field tests: pumping-out test, pumping-in test and the slug test.
The quick sand condition occurs when the upward seepage pressure equals the submerged weight of the soil; the critical hydraulic gradient ic = (G − 1)/(1 + e), which is about 1.0 for most sands, and the factor of safety against piping = ic/i.
In a flow net the flow lines and equipotential lines intersect at right angles; seepage q = kH(Nf/Nd) per metre width; flow nets are used to find seepage loss, uplift pressure, exit gradient and the pore pressure distribution.
Effective stress principle σ' = σ − u; a rise in the water table reduces the effective stress and hence the bearing capacity of the soil, while the total stress increases.
Capillary rise hc = 4Ts/(γw d) = 0.3/(e × D10) approximately; finer soils show greater capillary rise, and capillary moisture gives apparent cohesion to damp sand.
Compaction is the instantaneous densification of an unsaturated soil by mechanical energy, whereas consolidation is the gradual expulsion of pore water from a saturated soil under a sustained load.
Standard Proctor test: 2.6 kg rammer, 305 mm fall, 3 layers, 25 blows per layer (595 kJ/m³); Modified Proctor test: 4.9 kg rammer, 457 mm fall, 5 layers, 25 blows per layer (2693 kJ/m³).
The zero air void line is given by γd = Gγw/(1 + wG); the compaction curve approaches but can never cross the ZAV line because 100% saturation cannot be achieved by compaction.
With an increase in compactive effort the maximum dry density increases and the optimum moisture content decreases; the OMC increases with clay content and with the plasticity of the soil.
Field density tests: core cutter method (fine-grained cohesive soils), sand replacement (sand cone) method (cohesionless as well as cohesive soils) and the rubber balloon method.
Mohr-Coulomb failure criterion: τf = c + σ tan φ; the shear strength is determined by the direct shear, triaxial (UU, CU, CD), unconfined compression and vane shear tests.
In an unconfined compression test on saturated clay the undrained shear strength cu = qu/2; the test is a special case of the triaxial UU test with σ3 = 0 and is not suitable for cohesionless soils.
In a direct shear test the failure plane is horizontal and predetermined and the direction of the principal stresses rotates during shearing – the main limitations of the test; drainage and the rate of loading can, however, be controlled.
Triaxial test: the CD test gives the effective strength parameters c' and φ', the CU test gives total parameters (and effective ones if the pore pressure is measured) and the UU test gives the undrained strength with φ = 0 for saturated clay.
Rankine earth pressure: Ka = (1 − sin φ)/(1 + sin φ) = tan²(45° − φ/2), Kp = tan²(45° + φ/2), and Ka × Kp = 1; for φ = 30°, Ka = 1/3 and Kp = 3.
Active earth pressure is mobilised when the wall moves away from the backfill and passive pressure when it moves towards the backfill; the movement required to mobilise the full passive pressure is many times greater than that for the active pressure.
Coulomb's wedge theory assumes a planar failure surface and accounts for wall friction; Rankine's theory assumes a vertical, smooth wall with a horizontal backfill surface.
A retaining wall is checked for overturning (SF ≥ 2.0), sliding (SF ≥ 1.5), bearing capacity (SF ≥ 2.5–3.0) and for the maximum pressure at the toe not exceeding the allowable bearing pressure; a shear key increases the sliding resistance.
Terzaghi's general bearing capacity equation: qu = cNc + γDNq + 0.5γBNγ; for a purely cohesive soil (φ = 0), Nc = 5.7, Nq = 1 and Nγ = 0, so qu = 5.7c + γD.
The net ultimate bearing capacity qnu = qu − γD and the net safe bearing capacity = qnu/SF + γD; general shear failure occurs in dense sand and stiff clay, local shear failure in medium dense sand and punching shear failure in loose sand and soft clay.
The plate load test gives the allowable bearing pressure and the settlement in situ using plates of 300–750 mm size; it is not reliable for deep deposits because the depth of influence is only about 1.5–2 times the plate width.
In the standard penetration test the N-value is the number of blows for the last 300 mm of penetration after a 150 mm seating drive; the dilatancy correction is N' = 15 + ½(N − 15) when N > 15 for fine sand and silt below the water table.
In-situ tests: SPT, static cone penetration test (CPT), pressuremeter test, vane shear test, plate load test and field permeability tests; boring logs record the soil strata, water table depth, N-values and sample details.
The depth of soil exploration should extend at least to the depth where the increase in pressure due to the structural load is less than 10% of the existing effective overburden pressure.
Coefficient of consolidation cv = k/(mvγw) and time factor Tv = cv t/d²; Tv = 0.197 for 50% consolidation and 0.848 for 90% consolidation.
Skempton's empirical relation for the compression index of a normally consolidated clay: Cc = 0.009(LL − 10); the swelling index Cs is about Cc/5 to Cc/10.
Primary consolidation settlement Sc = [Cc H/(1 + e0)] log10[(σ0' + Δσ')/σ0'] for a normally consolidated clay; for over-consolidated clay the recompression index Cs is used up to the preconsolidation pressure.
Over-consolidation ratio OCR = preconsolidation pressure / present effective overburden pressure; OCR = 1 normally consolidated, OCR > 1 over-consolidated.
Total settlement = immediate (elastic) settlement + primary consolidation settlement + secondary consolidation (creep); secondary compression is important in organic soils and clays.
Shallow foundations: isolated (individual) footing, combined (rectangular or trapezoidal) footing, strap (cantilever) footing and raft (mat) foundation; a raft is adopted when the required footing area exceeds about 50% of the plan area or the soil is weak.
Deep foundations: piles (end bearing, friction, compaction, under-reamed), piers, caissons and open wells; the ultimate capacity of a pile = end bearing + skin friction − self weight.
Group efficiency of piles is less than 100% in cohesive soils (the group capacity is less than the sum of the individual capacities) but can exceed 100% in dense cohesionless soils; the settlement of a pile group is always greater than that of a single pile.
A negative skin friction develops on a pile when the surrounding soil settles more than the pile (for example, in newly filled ground or consolidating soft clay), and it reduces the load capacity of the pile.

Part 7: Fluid Mechanics & Hydraulics 216–26550 points

Density of water is 1000 kg/m³, specific weight γ = ρg = 9810 N/m³, and specific gravity is the ratio of the weight of a substance to the weight of an equal volume of water at 4 °C.
Dynamic viscosity μ is expressed in Pa·s (1 poise = 0.1 Pa·s) and kinematic viscosity ν = μ/ρ in m²/s (1 stoke = 10⁻⁴ m²/s); the viscosity of water at 20 °C is about 0.01 poise.
Newton's law of viscosity τ = μ(du/dy) is obeyed by Newtonian fluids such as water and air; blood, sewage sludge, paint and printer's ink are non-Newtonian fluids.
An ideal fluid is incompressible and non-viscous; a real fluid possesses viscosity; an ideal plastic (Bingham) fluid requires an initial yield stress before it starts to flow.
Surface tension causes capillarity; the capillary rise in a tube h = 4σcos θ/(ρgd), and for water in a clean glass tube the contact angle θ is nearly zero.
Vapour pressure increases with temperature; cavitation occurs when the local pressure falls below the vapour pressure, forming and collapsing vapour bubbles, which damages pumps, turbines, spillways and propellers.
Bulk modulus of elasticity K = −dp/(dV/V) and compressibility = 1/K; for water K is about 2.07 GPa.
Pascal's law: pressure applied to an enclosed fluid at rest is transmitted undiminished and equally in all directions.
Pressure head = p/γ; standard atmospheric pressure = 101.325 kN/m² = 10.33 m of water = 760 mm of mercury; gauge pressure = absolute pressure − atmospheric pressure.
Total pressure force on an immersed plane surface F = γA x̄, where x̄ is the depth of the centroid; the centre of pressure h* = x̄ + I_G/(A x̄) and always lies below the centroid.
For a vertical rectangular plane surface of depth d, the centre of pressure is at 2d/3 from the free surface; for a triangular surface with the vertex at the top it is at 3d/4.
Buoyant force equals the weight of the fluid displaced and acts through the centre of buoyancy (the centroid of the displaced volume); a floating body is stable when the metacentre lies above the centre of gravity, with BM = I/V.
The continuity equation A1V1 = A2V2 for steady incompressible flow is based on the principle of conservation of mass.
Bernoulli's equation p/γ + V²/2g + z = constant is based on the conservation of energy and applies along a streamline for steady, incompressible, non-viscous flow.
Assumptions of Bernoulli's equation: steady flow, incompressible fluid, non-viscous (no friction loss) and irrotational flow along the streamline.
In a venturimeter the convergent cone angle is 20–22° and the divergent cone angle 5–7° to avoid flow separation; the throat diameter is usually one-third to one-half of the pipe diameter.
The coefficient of discharge of an orificemeter is about 0.6 and that of a venturimeter 0.95–0.98; an orificemeter is cheaper but has a much higher permanent head loss.
A piezometer measures the static pressure of a liquid in a pipe; a Pitot tube measures the stagnation (total) pressure, and the point velocity V = √(2gh) from the difference of the two.
Rectangular notch Q = (2/3)Cd L √(2g) H^1.5; triangular (V) notch Q = (8/15)Cd tan(θ/2) √(2g) H^2.5 – the V-notch is more accurate for small discharges.
Weirs are classified as sharp-crested, broad-crested and ogee (spillway); for a suppressed rectangular weir the Francis formula is Q = 1.84 L H^1.5 in SI units.
A Cipoletti weir is a trapezoidal weir with side slopes of 1 horizontal to 4 vertical, which compensates for the end contractions.
Reynolds number Re = VD/ν: in pipes Re < 2000 laminar, 2000–4000 transitional and > 4000 turbulent; in open channels Re < 500 laminar and Re > 2000 turbulent.
Froude number Fr = V/√(gD): Fr < 1 sub-critical (tranquil), Fr = 1 critical and Fr > 1 super-critical (shooting) flow; for a rectangular channel the critical depth yc = (q²/g)^1/3.
For a rectangular channel at critical flow Vc = √(g yc) and the minimum specific energy E_min = 1.5 yc; specific energy E = y + V²/2g.
Hydraulic jump: the conjugate depth ratio y2/y1 = ½[√(1 + 8Fr1²) − 1] and the energy loss ΔE = (y2 − y1)³/(4y1y2); it is the basis of energy dissipation below spillways and weirs.
Types of hydraulic jump by the initial Froude number: 1–1.7 undular, 1.7–2.5 weak, 2.5–4.5 oscillating, 4.5–9 steady and above 9 strong (rocky) jump.
Chezy's formula V = C√(RS) and Manning's formula V = (1/n)R^2/3S^1/2; typical Manning's n values are 0.013 for smooth concrete, 0.015 for RCC, 0.0225 for a well-maintained earthen canal and 0.03–0.04 for a natural river.
The most economical rectangular section has b = 2y and R = y/2; for the most economical trapezoidal section half the top width equals the sloping side and R = y/2.
For the most economical triangular section the side slopes are at 45° (m = 1); for the most economical trapezoidal section the side slope is 60° with the horizontal (m = 1/√3).
Gradually varied flow profiles: M1 (backwater curve, above an obstruction such as a weir), M2 and M3 on a mild slope; S1, S2 (drawdown at the entrance of a steep channel) and S3 on a steep slope; H2, H3 horizontal and A2, A3 adverse slope profiles.
Darcy-Weisbach head loss hf = fLV²/(2gD) with f = 64/Re for laminar flow; major losses are due to friction and minor losses to entrance, exit, bends, valves and sudden changes of section.
Loss at sudden enlargement (Borda-Carnot) = (V1 − V2)²/2g; loss at the entrance of a pipe = 0.5V²/2g and loss at the exit = V²/2g.
Water hammer: for an instantaneous valve closure the pressure rise Δp = ρcV, where c is the velocity of the pressure wave; water hammer occurs when the time of closure is less than 2L/c.
Pipes in series carry the same discharge and the head losses are additive; pipes in parallel have the same head loss and the discharges are additive.
The hydraulic gradient line (HGL) joins the piezometric heads and the total energy line (TEL) is the HGL plus the velocity head; the TEL is always above the HGL and both slope downward in the direction of flow.
A siphon carries liquid over an obstruction higher than the supply level; the pressure at the summit must remain above the vapour pressure, and the maximum practical suction lift of a centrifugal pump is about 7–8 m of water.
Force exerted by a jet on a stationary flat plate held normal to it is F = ρAV²; on a plate inclined at θ to the jet, F = ρAV² sin θ normal to the plate.
In an open channel the flow is measured with a current meter, Parshall flume, weir, notch or float method; a rating (stage-discharge) curve relates the gauge height to the discharge as Q = K(H − a)ⁿ.
Buckingham's π-theorem: the number of dimensionless π-terms = total number of variables − number of fundamental dimensions; Reynolds, Froude, Euler, Weber and Mach numbers are the important dimensionless parameters.
Model laws: Froude's law for free-surface flows (spillways, weirs, ships, rivers), Reynolds' law for pipe flow and submerged bodies, and Mach's law for compressible flow; distorted models are used for rivers.
In a boundary layer the flow is laminar near the leading edge and turbulent downstream; separation of the boundary layer occurs in a region of adverse pressure gradient (dp/dx > 0).
For laminar flow in a circular pipe the velocity profile is parabolic, u_max = 2V_avg, and the shear stress varies linearly from zero at the centre to a maximum at the wall.
Drag on a body = pressure (form) drag + skin friction drag; streamlining reduces the form drag, and terminal velocity is reached when the drag plus buoyancy equals the weight.
A centrifugal pump suits high discharge and low head while a reciprocating pump suits low discharge and high head; a centrifugal pump must be primed before starting and NPSH available must exceed the NPSH required.
Specific speed of a centrifugal pump Ns = N√Q/H^3/4 and of a turbine Ns = N√P/H^5/4; a higher specific speed implies a lower head and a larger discharge.
Turbine selection: Pelton for high head (above about 250 m) and low discharge, Francis for medium head (40–250 m) and Kaplan/propeller for low head (below 40 m) with large discharge.
A draft tube is a diverging conduit at the outlet of a reaction turbine; it recovers the kinetic energy of the exiting water, increases the effective head and permits the turbine to be set above the tail race level.
A surge tank is provided between the head race (or penstock) and the turbine in high-head plants to relieve water hammer and to supply additional water during a sudden increase of load.
In anisotropic soils (kx ≠ ky) the flow-net section is transformed by multiplying all horizontal dimensions by √(kx/ky) before drawing the net, and the seepage is computed with the equivalent permeability √(kx ky).
The most economical section (best hydraulic section) gives the maximum discharge for a given area, slope and roughness, which corresponds to the minimum wetted perimeter and hence the minimum lining cost.

Part 8: Hydrology, Irrigation Demand & Water Resources 266–30035 points

The hydrologic cycle consists of precipitation, interception, infiltration, evaporation, transpiration, runoff and groundwater flow; the water balance equation is P − R − G − ET = ΔS.
A non-recording (Symon's) rain gauge gives only the total depth of rainfall for the period, whereas tipping bucket, siphon (float) and weighing bucket gauges give the intensity of rainfall (a hyetograph).
The consistency of a rainfall record is checked by the double mass curve, and missing data are estimated by the normal ratio method or the inverse square distance method.
Areal rainfall is computed by the arithmetic mean, Thiessen polygon or isohyetal method; the isohyetal method is the most accurate because it takes the topography into account.
Evaporation is measured with a USWB Class A pan with a pan coefficient of about 0.7; evapotranspiration is estimated by the Penman, modified Penman (FAO-56 Penman-Monteith) or Blaney-Criddle methods.
The infiltration capacity decreases with time to a constant value; Horton's equation f = fc + (f0 − fc)e^−kt; the φ-index = (P − R)/t and the w-index = (P − R − I)/t.
The rational formula Q = (1/3.6) K Pc A I (Q in m³/s, A in km², I in mm/h) gives the peak discharge, where Pc is the runoff (imperviousness) coefficient and K a unit conversion factor.
A unit hydrograph is the hydrograph of direct runoff due to 1 cm of effective rainfall falling uniformly over the basin in a specified duration; its assumptions are linearity, time invariance and uniform distribution of rainfall.
An S-curve is obtained by summing successive unit hydrographs spaced by the unit duration and is used to derive a unit hydrograph of a different duration.
A synthetic unit hydrograph (Snyder's method) is derived from the basin area, lag time and empirical coefficients and is used for ungauged catchments.
For separating the base flow from the direct runoff, the time from the peak to the end of direct runoff is often taken as N = 0.84 A^0.2 days, with A in km².
Flood frequency analysis uses Gumbel's extreme value distribution, log-Pearson Type III or the log-normal distribution; return period T = 1/P and the risk of exceedance in n years = 1 − (1 − 1/T)ⁿ.
A mass curve (Rippl's diagram) gives the storage requirement of a reservoir, a flow-duration curve shows the percentage of time a given discharge is equalled or exceeded, and area-elevation and capacity-elevation curves are used for reservoir capacity computation.
Trap efficiency of a reservoir depends on the capacity-to-inflow ratio; sedimentation first fills the dead storage and progressively reduces the live storage and the useful life of the project.
An unconfined aquifer has a free water table and a confined aquifer is under artesian pressure; specific yield Sy = volume of water drained by gravity / total volume, and specific retention is the water held back.
For steady radial flow to a fully penetrating well in an unconfined aquifer, Dupuit's equation gives Q = πk(H² − h²)/ln(R/r); the specific capacity of a well is the discharge per unit drawdown.
Sediment is transported as bed load (rolling, sliding and saltation), suspended load (supported by turbulence) and wash load; Lacey's silt factor f = 1.76√d (d in mm) and the regime scour depth R = 0.47(Q/f)^1/3.
The rising limb, crest segment and recession limb make up a hydrograph; the peak discharge occurs when the duration of the rainfall equals the time of concentration of the basin.
Flood routing is of two types: reservoir (level pool) routing and channel (Muskingum) routing, with the Muskingum storage equation S = K[xI + (1 − x)Q] where x = 0 to 0.5 (usually 0.2–0.3).
The crop water requirement ETc = Kc × ET0, where Kc is the crop coefficient and ET0 the reference evapotranspiration; the design flood may be the standard project flood (SPF) or the probable maximum flood (PMF).
The antecedent moisture condition, soil type, land use and rainfall intensity govern the runoff; the SCS curve number method is widely used for estimating runoff from ungaged catchments.
A dependable (firm) yield is the yield available with a specified probability of exceedance (for example a 90% dependable flow); energy generated on the basis of firm flow is firm energy and the excess is secondary energy.
Groundwater recharge occurs by infiltration of rainfall, seepage from canals and reservoirs, and induced recharge from rivers; over-draft causes a falling water table, drying of springs and land subsidence.
Watershed management reduces runoff, soil erosion and sediment yield through afforestation, contour bunding, terracing, check dams and gully control.
Water balance of an irrigation command area: water diverted − conveyance losses − field losses = water stored/consumed; the irrigation efficiency is the ratio of the water beneficially used to the water diverted.
Duty D (hectares per cumec) and delta Δ (depth of water in metres) are related by Δ = 8.64 B/D, where B is the base period in days.
The base period is the time between the first and the last watering of a crop; the kor period is the initial watering period and the kor depth is the depth of water applied during it.
In Nepal the main kharif (monsoon) crops are paddy, maize and sugarcane and the rabi (winter) crops are wheat, barley, mustard and pulses; the crop period and the base period differ for each crop.
Irrigation methods: flooding (free, check, border), furrow, basin, sub-surface, sprinkler and drip; drip irrigation has the highest water use efficiency (about 90%) and suits water-scarce areas and row crops.
Irrigation efficiencies: conveyance, application, storage and use efficiency; the overall (project) efficiency = conveyance efficiency × application efficiency.
Available moisture = field capacity − wilting point; the readily available moisture is about 75–80% of the available moisture and irrigation is applied when the depletion reaches this limit.
The frequency of irrigation depends on the available moisture of the soil, the root zone depth, the rate of evapotranspiration and the effective rainfall.
Waterlogging is the saturation of the root zone by a rising water table; its causes are over-irrigation, seepage from canals, obstruction of natural drainage and heavy rainfall, and its effects are salinity, poor aeration and reduced crop yields.
Agricultural drainage is surface (open drains) or subsurface (tile and mole drains); the spacing of tile drains is determined by Hooghoudt's equation using the permeability, depth of the impervious layer and drain discharge.
Reclamation of waterlogged and saline land requires subsurface drainage, leaching of salts, controlled irrigation, gypsum application for sodic soils and the cultivation of salt-tolerant crops.

Part 9: Structural Mechanics & Theory of Structures 301–36060 points

Stress = P/A and strain = δL/L; Young's modulus E = stress/strain and Hooke's law holds up to the proportional limit.
The sequence of points on a mild steel stress-strain curve is: proportional limit, elastic limit, upper yield point, lower yield point, ultimate stress and the breaking point.
For materials without a definite yield point (aluminium, high-strength steel) the yield strength is defined by the 0.2% proof (offset) strain method.
Ductility is measured by percentage elongation and reduction in area, toughness by the total area under the stress-strain curve, resilience by the area up to the elastic limit (modulus of resilience = σy²/2E) and brittleness by the impact strength.
Poisson's ratio ν = lateral strain/longitudinal strain: 0.25–0.33 for most metals, 0.5 for rubber and nearly 0 for cork; E = 2G(1 + ν) = 3K(1 − 2ν).
When thermal expansion is fully prevented the thermal stress σ = EαΔT (compressive for a rise in temperature); in a compound bar the load is shared in proportion to EA of each part.
Principal stresses σ1,2 = (σx + σy)/2 ± √[((σx − σy)/2)² + τxy²] and the principal planes are at θp = ½ tan⁻¹[2τxy/(σx − σy)]; no shear stress acts on a principal plane.
Maximum shear stress τ_max = (σ1 − σ2)/2 and it acts on planes inclined at 45° to the principal planes.
In Mohr's circle the radius equals τ_max, the centre is at [(σx + σy)/2, 0], and angles on the circle are twice the corresponding physical angles.
Thin cylinder: hoop stress σh = pd/2t and longitudinal stress σl = pd/4t, so the hoop stress is twice the longitudinal stress; a cylinder is treated as thin when t < d/20.
In a thick cylinder (Lame's theory) the hoop stress is maximum (tensile) at the inner surface and the radial stress is maximum (compressive) at the inner surface and zero at the outer surface.
Torsion formula T/J = τ/r = Gθ/L; the polar modulus of a solid shaft Zp = πd³/16 and the power transmitted P = 2πNT/60 watts.
For the same weight a hollow shaft transmits more torque than a solid shaft, because in torsion the material near the centre is under-utilised.
Close-coiled helical spring: deflection δ = 64WR³n/(Gd⁴) and stiffness k = Gd⁴/(64R³n); springs in series add their compliances (1/k) and springs in parallel add their stiffnesses.
The simple bending (flexure) equation is M/I = σ/y = E/R; its assumptions are a homogeneous, isotropic, initially straight beam, plane sections remaining plane and stresses within the elastic limit.
The section modulus measures the bending strength of a section; for the same cross-sectional area an I-section is more economical than a rectangular section.
Shear stress τ = VQ/(Ib); the maximum shear stress is 1.5 times the average for a rectangle and 4/3 times the average for a circle, and in an I-section it occurs in the web at the neutral axis.
Slope and deflection are found by the double integration method, Macaulay's method, the moment-area method, the strain energy (Castigliano) method and the unit load (virtual work) method.
Standard deflections: cantilever with UDL δ = wL⁴/(8EI); simply supported beam with a central point load δ = WL³/(48EI) and with UDL δ = 5wL⁴/(384EI).
Deflection is inversely proportional to the flexural rigidity EI; the maximum deflection occurs where the slope is zero.
Euler's crippling load P = π²EI/Le², with the effective length Le = L for both ends hinged, L/2 for both ends fixed, 2L for one end fixed and the other free, and L/√2 for one end fixed and the other hinged.
Rankine-Gordon formula 1/P = 1/Pc + 1/Pe combines crushing and buckling; short columns fail by crushing and long (slender) columns by buckling, the slenderness ratio λ = Le/k deciding the mode.
A column buckles about the axis having the least radius of gyration (least moment of inertia).
Strain energy: P²L/(2AE) for an axial load, ∫M²dx/(2EI) for bending and T²L/(2GJ) for torsion; Castigliano's first theorem: δ = ∂U/∂P.
Maxwell's reciprocal theorem (deflection at i due to a load at j equals the deflection at j due to the same load at i) and Betti's law apply to linearly elastic structures; the flexibility coefficients satisfy fij = fji.
Static indeterminacy: plane truss Ds = m + r − 2j; plane frame Ds = 3m + r − 3j. Kinematic indeterminacy: plane truss 2j − r and plane frame 3j − r (reduced by the number of members if axial deformation is neglected).
Members of an ideal truss carry only axial force; the method of joints uses the equilibrium of each joint and the method of sections cuts not more than three unknown members.
Zero-force members: at a joint with two non-collinear members and no external load both are zero-force members; at a joint with three members, two of which are collinear and no load, the third is a zero-force member.
Common trusses are Warren, Pratt, Howe, Fink, Belgian and scissors; in a Pratt truss the diagonals are in tension and the verticals in compression, which is why the longer diagonals are used in tension.
Influence lines for a simply supported beam: the reaction ILD is a straight line varying from 1 at the support to 0 at the other end; the bending moment ILD at a section is triangular with a peak of ab/L; the shear ILD consists of two rectangles of height a/L and b/L.
For a UDL longer than the span the maximum bending moment at a section occurs when the whole span is loaded; for a load shorter than the span it occurs when the section divides the load in the same ratio as it divides the span.
Muller-Breslau principle: the influence line for any stress function is proportional to the deflected shape obtained by removing the corresponding restraint and applying a unit displacement in its direction.
The absolute maximum bending moment in a simply supported beam due to a series of moving wheel loads occurs under one of the loads when that load and the resultant of all the loads on the span are equidistant from the centre of the span.
A two-hinged parabolic arch carrying a uniformly distributed load over the whole span has zero bending moment at every section (pure compression); the horizontal thrust H = wL²/(8h).
A three-hinged arch is statically determinate; a two-hinged arch is statically indeterminate to the first degree and a fixed arch to the third degree.
The rise-to-span ratio of an arch is usually between 1/5 and 1/10; as the rise increases the horizontal thrust decreases but the length of the arch rib increases.
A cable carrying a uniformly distributed load over a horizontal span takes a parabolic shape; the horizontal tension H = wL²/(8h) and the maximum tension occurs at the supports.
The slope-deflection method is a stiffness (displacement) method in which the joint rotations and translations are the unknowns: MAB = MFAB + (2EI/L)(2θA + θB − 3Δ/L).
Moment distribution (Hardy Cross) method: distribution factor DF = K/ΣK and the carry-over factor is 0.5 for a prismatic member with the far end fixed and zero when the far end is hinged.
Fixed end moments: wL²/12 at both ends for a fixed beam with UDL, WL/8 for a central point load, and wL²/8 at the fixed support of a propped cantilever with UDL.
Rotational stiffness K = 4EI/L for a member with the far end fixed and 3EI/L when the far end is hinged.
Conjugate beam method: the shear at a point of the conjugate beam equals the slope of the real beam and the bending moment of the conjugate beam equals the deflection of the real beam.
In plastic analysis the shape factor S = Zp/Ze and the load factor = S × factor of safety; the collapse load is found by the statical (lower bound), kinematic (upper bound) or mechanism method.
A plastic hinge forms at the section of maximum bending moment; the number of plastic hinges required to cause collapse = degree of static indeterminacy + 1.
Collapse loads: simply supported beam with a central load Wc = 4Mp/L; fixed beam with a central load Wc = 16Mp/L; propped cantilever with UDL wc = 11.66 Mp/L².
Sway occurs in a portal frame when the geometry or the loading is unsymmetrical; for a regular multi-storey frame the number of independent sway mechanisms equals the number of storeys.
Approximate methods for building frames: substitute frame method for vertical loads, portal method for lateral loads (interior columns take twice the shear of exterior columns) and cantilever method for tall frames (axial forces proportional to the distance from the centroidal axis).
Seismic design: base shear Vb = Ah W with Ah = (Z/2)(I/R)(Sa/g), where Z is the zone factor, I the importance factor, R the response reduction factor and Sa/g the spectral acceleration coefficient (NBC 105 / IS 1893).
Ductile detailing requires closely spaced confinement ties in the plastic hinge zones, restrictions on lap splices and a strong column-weak beam concept (NBC 205 / IS 13920).
The natural frequency of a single-degree-of-freedom system ω = √(k/m); resonance occurs when the forcing frequency equals the natural frequency and damping limits the response.
Logarithmic decrement δ = (1/n) ln(x1/xn+1) and the damping ratio ζ = δ/√(4π² + δ²); the dynamic magnification factor of an undamped system is 1/(1 − r²) with r = ω/ωn.
For a load applied eccentrically the stress = P/A ± M/Z; for no tension to develop in a rectangular section the load must lie within the middle third (the kern is b/6 and d/6 from the centroid).
For a solid circular section the kern (core) is a circle of diameter d/4; for a hollow circular section it is a circle of diameter (D² + d²)/(4D).
For combined bending and torsion the equivalent torque Te = √(M² + T²) and the equivalent bending moment Me = ½[M + √(M² + T²)].
A suddenly applied load produces twice the stress produced by the same load applied gradually; for a load falling through a height h, σ = σstatic[1 + √(1 + 2h/δ)].
Fatigue failure occurs under repeated or reversed stresses well below the ultimate strength; the endurance limit is the stress below which a material can withstand an infinite number of cycles, and stress concentration greatly reduces it.
Creep is the time-dependent deformation under a sustained load; in concrete it increases deflection and causes loss of prestress, while in steel it becomes important at high temperatures.
Cold working and strain hardening increase the yield strength and hardness of steel but reduce its ductility and toughness.
Impact tests (Charpy, Izod) measure toughness, hardness tests (Brinell, Rockwell, Vickers) measure resistance to indentation, and the rotating beam test determines the endurance limit.
In a beam the point of contraflexure is where the bending moment changes sign (BM = 0) and the point of maximum bending moment is where the shear force changes sign (SF = 0).

Part 10: Design of Structures: Concrete, RCC, Steel, Timber & Masonry 361–41555 points

Loads on a structure: dead load, imposed (live) load, wind load, snow load and earthquake load; typical load combinations are 1.5(DL + LL), 1.5(DL + EL) and 1.2(DL + LL + EL) (NBC 102 / IS 875 and IS 1893).
Minimum imposed (live) loads on floors: about 2 kN/m² for residential rooms, 2.5–3 kN/m² for offices, 3–4 kN/m² for stairs and corridors and 4–5 kN/m² for assembly areas.
In the working stress method the modular ratio m = 280/(3σcbc); for M20 concrete σcbc = 7 N/mm² and for Fe 415 steel σst = 230 N/mm².
In the limit state method the partial safety factors are 1.5 for concrete and 1.15 for steel; the characteristic strength is the 5% fractile below which not more than 5% of the results are expected to fall.
Limit states: limit state of collapse (flexure, shear, torsion, compression) and limit state of serviceability (deflection, cracking and vibration).
Serviceability limits: maximum deflection span/250 and maximum crack width 0.3 mm for moderate exposure, 0.2 mm for severe and 0.1 mm for very severe exposure.
Minimum cover to reinforcement (IS 456): 20 mm mild, 30 mm moderate, 45 mm severe and 50 mm very severe exposure; nominal cover is generally 20 mm for slabs, 25 mm for beams, 40 mm for columns and 50 mm for footings.
Minimum tension reinforcement in a beam Ast = 0.85bd/fy and the maximum tension steel is 4% of the gross area; in a column the minimum steel is 0.8% (0.8% to 6%, or 4% where bars are not lapped) of the gross area.
Minimum reinforcement in a slab is 0.12% of the gross area for HYSD bars and 0.15% for mild steel bars.
Limiting depth of the neutral axis xu,max/d = 0.53 for Fe 250, 0.48 for Fe 415 and 0.46 for Fe 500; the corresponding limiting moment coefficients Mu,lim/(fck bd²) are 0.148, 0.138 and 0.133.
Under-reinforced sections are preferred because the steel yields before the concrete crushes, giving ample warning (large deflection and wide cracks) before failure.
Nominal shear stress τv = Vu/(bd) must be less than τc,max; shear reinforcement is provided when τv exceeds the design shear strength of concrete τc, and the maximum spacing of vertical stirrups is limited to 0.75d or 300 mm, whichever is less.
Shear reinforcement is provided as vertical stirrups, bent-up bars or inclined bars; bent-up bars alone are not sufficient for shear unless they are used together with vertical stirrups.
Development length Ld = φσs/(4τbd); the design bond stress τbd for plain bars in tension is 1.2 N/mm² for M20 concrete, increased by 60% for deformed (HYSD) bars and by 25% for bars in compression.
Anchorage value of bends: 4φ for each 45° of bend subject to a maximum of 16φ (a 90° hook 8φ, a 135° hook 12φ and a 180° standard U-hook 16φ less deductions).
Lap length: tension lap = Ld or 30φ whichever is greater; compression lap = Ld or 24φ whichever is greater; laps are staggered and located at sections of low stress.
A slab is designed as a one-way slab when ly/lx > 2 and as a two-way slab when ly/lx ≤ 2; the maximum spacing of bars in a slab is 3d or 300 mm for main bars and 5d or 450 mm for distribution bars.
Basic span-to-effective-depth ratios for deflection control: 7 for a cantilever, 20 for a simply supported span and 26 for a continuous span up to 10 m.
Torsion in RCC is designed by the space truss (skew bending) analogy using an equivalent shear force and an equivalent bending moment.
A column is short when both slenderness ratios lex/b and ley/D are less than 12; a short column fails by crushing and a slender column by buckling.
The minimum eccentricity to be considered in a column is emin = L/500 + b/30 or 20 mm, whichever is greater.
Minimum number of longitudinal bars: 4 for a rectangular column, 3 for a triangular and 6 for a circular column; a column with helical reinforcement can carry 5% more load than one with lateral ties.
In an isolated footing the critical section for bending is at the face of the column, for one-way shear at a distance d from the face of the column and for two-way (punching) shear at d/2 from the face.
A combined footing is used when the column spacing is small, when a footing is restricted by the property line, or to obtain a uniform soil pressure; a strap (cantilever) footing joins two footings by a rigid beam that does not bear on the soil.
Pre-tensioning: the tendons are tensioned before the concrete is cast and the prestress is transferred by bond (factory precasting); post-tensioning: the tendons are tensioned after the concrete has hardened and the prestress is transferred by the end anchorages.
Losses of prestress: elastic shortening of concrete, creep, shrinkage, relaxation of steel, friction (post-tensioning) and anchorage slip; the total loss is about 20% for pre-tensioned and 15–18% for post-tensioned members.
Post-tensioning systems: Freyssinet, Magnel-Blaton, Gifford-Udall, CCL, BBRV and Lee-McCall; Guyon's load-balancing concept is used for cable profile selection.
In steel structures the yield stress of Fe 410 (E 250) grade steel is 250 MPa; bolts are of grades 4.6, 8.8 and 10.9, the first number being the ultimate strength in hundreds of MPa and the second the ratio of yield to ultimate strength.
Bolted connections are bearing type or friction type (HSFG); the efficiency of a joint is the least of the strengths in tearing of the plate, shearing of the bolt and bearing of the plate divided by the strength of the solid plate.
Welds: fillet, butt (single or double V), slot and plug; the effective throat thickness of a fillet weld = 0.7 × the leg length, and the size of a fillet weld should not exceed the thickness of the thinner part minus 1.5 mm.
A welded joint can attain 100% efficiency, is lighter and quieter than a riveted joint and requires no drilling, but it cannot be inspected easily and is sensitive to poor workmanship.
Tension members are designed on the net effective area; angles connected through one leg suffer shear lag, which is accounted for by a reduction factor β.
Effective length factors K for compression members (IS 800): 0.65 both ends fixed, 0.80 one end fixed and the other pinned, 1.00 both ends pinned and 2.00 one end fixed with the other free; the slenderness limit is 180 for compression members and 400 for tension members.
In a built-up column the slenderness of the lacing bar should not exceed 145, the lacing is inclined at 40°–70° (preferably 60°) to the axis, and tie plates are provided at the ends and at intermediate points.
Column bases: slab base for light loads and gusseted base for heavy loads; the bearing pressure on the concrete pedestal should not exceed 0.45 fck multiplied by √(A1/A2).
In a plate girder the flanges resist the bending moment and the web resists the shear; vertical and horizontal stiffeners are provided to prevent web buckling, and the depth of the girder is usually 1/8 to 1/12 of the span.
A roof truss consists of principal rafters, purlins and tie members; the spacing of trusses is usually 1/4 to 1/5 of the span and the truss is designed for dead, live and wind loads.
Timber is much stronger in tension and compression parallel to the grain than perpendicular to it; the permissible stresses are reduced for long columns using a slenderness reduction, and timber joints include mortise and tenon, dovetail, scarf and bridle joints.
Timber defects: knots, shakes, splits, twists, cupping and dry rot; preservation is done with creosote oil, ASCU (arsenic-copper-chromium) or zinc chloride, and seasoning is done by air, kiln, water or boiling.
In unreinforced masonry the tensile strength is neglected; masonry is strong in compression but weak in tension and shear, so it performs poorly in earthquakes unless confined by RCC bands and properly interlocked.
Earthquake-resistant features of masonry buildings (NBC 105 / IS 4326): plinth band, lintel band, roof band, vertical reinforcement at corners and openings, and a proper bond between intersecting walls.
Mortar proportions: cement mortar 1:3 to 1:6, lime mortar 1:2 to 1:3 and mud mortar for rural construction; cement mortar should be used within about 30 minutes of mixing.
Concrete mix design (IS 10262): target mean strength f't = fck + 1.65s; the maximum water-cement ratio and the minimum cement content are governed by durability and exposure conditions.
Durability requirements (IS 456): mild exposure M20 with w/c 0.55, moderate M25/0.50, severe M30/0.45, very severe M35/0.45 and extreme M40/0.40.
Quality control of concrete requires sampling, cube tests at 7 and 28 days, comparison with the characteristic strength, standard deviation, and non-destructive tests when doubt arises.
Ready-mix concrete should normally be discharged within about 90 minutes to 2 hours of the first addition of water; retarders are used to extend this time in hot weather.
Stripping of formwork: vertical sides of beams and columns 16–24 hours, slab soffits (props left) 3 days, beam soffits 7 days, props to slabs spanning up to 4.5 m 7 days, props to slabs spanning over 4.5 m 14 days, and props to beams and arches spanning over 6 m 21 days.
Detailing: at least two bars must be provided at the bottom of a beam, bars are curtailed where they are no longer required beyond the envelope of the bending moment diagram plus the development length, and hooks are provided at the ends of stirrups and main bars.
A bar bending schedule lists the bar mark, diameter, shape, cutting length, number of bars and weight; the unit weight of a steel bar = d²/162 kg/m with d in mm.
Corrosion of reinforcement is caused by chloride attack and carbonation of concrete; adequate cover and dense, impermeable concrete are the primary means of protection.
Strengthening and retrofitting methods: RC jacketing, steel plate bonding, fibre-reinforced polymer (FRP) wrapping, grouting and epoxy injection of cracks, and addition of shear walls or bracing.
Nepal National Building Code (NBC) parts: 101–105 cover scope, loads, symbols, terminology and seismic design; 201–208 cover materials and the design of concrete, masonry, timber and steel structures; and the 300-series covers services, fire safety and construction practices.
Wind load depends on the basic wind speed of the zone, the terrain (surface roughness) category, the height of the structure, the topography and the shape of the building; NBC 102 gives the basic wind speeds for different parts of Nepal.
Snow load is considered in the hilly and Himalayan regions of Nepal and is added to the roof live load in the load combination; the intensity reduces with the slope of the roof.
Deflection of a reinforced concrete member is computed using the effective modulus and the effective moment of inertia (cracked section); long-term deflection due to creep and shrinkage is obtained by a long-term factor.

Part 11: Water Supply, Sanitation & Environment 416–46550 points

The design per capita demand for an urban piped water supply in Nepal is generally 135 litres per capita per day (lpcd), while rural piped schemes are designed for about 45–70 lpcd.
Variation in demand: the maximum daily demand is about 180% of the average daily demand and the maximum hourly demand on the maximum day is about 270% of the average; the distribution system is designed for the maximum hourly demand.
Population forecasting methods: arithmetic increase, geometric increase, incremental increase, logistic curve and graphical comparison; the geometric increase method is suitable for young and rapidly growing cities.
Fire demand formulae: Kuelling Q = 3180√P, Freeman Q = 1136(P/10 + 10) and the National Board formula Q = 4630√P(1 − 0.01√P), where P is the population in thousands and Q is in litres per minute.
Hardness: temporary (carbonate) hardness is removed by boiling or lime softening and permanent (non-carbonate) hardness by the lime-soda process or ion exchange; hardness is expressed as mg/l of CaCO3 equivalent.
Drinking water standards (BIS 10500 / Nepal NDWQS): pH 6.5–8.5, turbidity 1 NTU, TDS 500 mg/l, chloride 250 mg/l, nitrate 45 mg/l, fluoride 1.0 mg/l, iron 0.3 mg/l and no coliforms in 100 ml.
The arsenic limit in drinking water is 0.01 mg/l as per WHO (an interim limit of 0.05 mg/l is used in some South Asian countries), and a free residual chlorine of 0.2–0.5 mg/l is required at the point of use.
Water-borne diseases: cholera, typhoid, bacillary dysentery, hepatitis A and E, poliomyelitis and guinea worm; water-washed diseases include trachoma and scabies, and water-based diseases include schistosomiasis.
Types of intake: river intake (tower, exposed, sump well), canal intake, reservoir intake, lake intake, infiltration gallery and spring tapping; the intake should be located upstream of pollution sources in a straight reach of the river.
Distribution systems: dead-end (tree) system – cheap and easy to design but water stagnates at the dead ends; grid-iron (looped) system – better circulation and fewer dead ends but more valves and cost; also ring and radial systems.
Pipe materials: cast iron, ductile iron, steel, asbestos cement, PVC/HDPE and RCC; the Hazen-Williams formula is generally used for plastic pipes and the Darcy or Manning formula for the others.
Pipe joints: socket and spigot, flanged, expansion, welded and mechanical (flexible) joints; lead-caulked joints are used for CI pipes and push-on rubber ring joints for DI pipes.
Valves and fittings: sluice (gate) valve for isolation, air release valve at the highest point, scour valve at the lowest point, reflux (check) valve to prevent backflow, pressure-reducing valve and fire hydrants.
A break pressure tank is provided in a gravity main where the static head exceeds the pressure rating of the pipe; it breaks the pressure head and prevents damage and water hammer.
The capacity of a service reservoir = balancing storage (usually about one-third of the daily supply) + fire storage + breakdown (emergency) reserve (about 10–25%); the mass curve method is used to determine the balancing storage.
Types of service reservoir: ground level (GLSR), elevated (OHSR) and underground; an elevated tank gives a constant pressure head in the distribution system.
The conventional treatment sequence for surface water is: screening → aeration → coagulation → flocculation → sedimentation → filtration → disinfection.
The detention period of a plain sedimentation tank is 2–4 hours and that of a coagulation cum sedimentation tank 2–4 hours; the surface overflow (detention) rate is about 500–1000 lph/m².
Coagulants: alum (aluminium sulphate, optimum pH 6.5–8.5), copperas, chlorinated copperas, ferric chloride and sodium aluminate; the optimum dose is determined by the jar test and coagulation removes colloidal turbidity, colour and bacteria.
Flocculation is gentle stirring that agglomerates the floc; the velocity gradient G = √(P/(μV)), typical values being G = 30–70 s⁻¹, Gt = 10⁴–10⁵ and a detention period of 20–30 minutes.
Types of settling: Type I discrete (dilute, non-flocculent), Type II flocculent, Type III hindered (zone) settling and Type IV compression settling.
Stokes' law settling velocity vs = g(G − 1)d²/(18ν) is valid for particles smaller than about 0.1 mm and Re < 1; a particle is completely removed if its settling velocity equals or exceeds the overflow rate Q/A.
A slow sand filter works at 100–200 lph/m², relies on the biological schmutzdecke and removes 98–99% of bacteria without coagulation; a rapid sand filter works at 3000–6000 lph/m² and requires coagulation and backwashing.
Filter media are specified by the effective size and the uniformity coefficient UC = D60/D10: slow sand filters 0.2–0.3 mm with UC 3–5, and rapid sand filters 0.35–0.55 mm with UC 1.3–1.7.
A rapid sand filter is backwashed when the head loss reaches 2.5–3.5 m or the effluent turbidity rises; the wash water required is about 2–6% of the filtered water.
Disinfection methods: chlorination, ozonation, ultraviolet radiation, boiling, iodine and silver treatment; the required residual chlorine is 0.2 mg/l after one hour of contact.
Breakpoint chlorination is the point at which the further addition of chlorine produces a proportional increase in the free residual chlorine; before this point the residual is combined (chloramines).
Chlorine demand = chlorine dose − residual chlorine; bleaching powder contains about 33% available chlorine and the contact period should not be less than 20–30 minutes.
Softening is done by the lime-soda process, ion exchange (zeolite), reverse osmosis or electrodialysis; iron and manganese are removed by aeration followed by filtration.
Aeration removes carbon dioxide, hydrogen sulphide, iron, manganese and volatile organic matter and improves taste and odour; the types are cascade (gravity), spray, diffused air and mechanical aerators.
In a separate sewerage system the sanitary sewage and storm water are carried separately, while in a combined system they share the sewer; a separate system is generally economical where rainfall is heavy.
A sewer is designed to run full at the maximum hourly (peak) flow, which is about 2–3 times the average dry weather flow.
The self-cleansing velocity is the velocity at which suspended solids neither settle nor the sewer scours – a minimum of 0.75 m/s and normally 0.9 m/s for sanitary sewers; the velocity should not exceed about 3 m/s.
Sewer shapes: circular (best hydraulic section), egg-shaped (better for combined sewers because it gives a higher velocity at low flow), horse-shoe and parabolic; materials used are RCC, vitrified clay (stoneware), PVC, cast iron and brick.
Sewer appurtenances: manholes at changes of direction, gradient, size and at regular intervals of 30–300 m; catch basins, street inlets, drop manholes, lamp holes, flushing tanks and grease traps.
BOD is the oxygen required by micro-organisms to stabilise the biodegradable organic matter (BOD5 at 20 °C is the standard test); COD measures both biodegradable and non-biodegradable organics, so COD is always greater than BOD.
First-order BOD reaction y = L(1 − 10^−kt) with k = 0.1 per day at 20 °C; BOD5 is about 68% of the ultimate BOD and k increases with temperature as kT = k20 × 1.047(T − 20).
Primary treatment removes 30–40% of the BOD and 50–70% of the suspended solids; secondary (biological) treatment removes 80–90% of the BOD; tertiary treatment removes nutrients, residual organics and pathogens.
Bar screens (coarse screens, clear spacing about 25–50 mm when manually cleaned and 20–25 mm when mechanically cleaned) remove floating matter; a grit chamber removes inorganic grit at a flow velocity of 0.15–0.3 m/s with a detention period of 30–60 seconds.
Types of grit chamber: horizontal flow, aerated and detritus tank; a proportional flow (Sutro) weir is used to maintain a constant velocity of 0.3 m/s in the chamber.
A primary sedimentation tank is designed for a detention period of 2–2.5 hours and a surface overflow rate of 25–35 m³/m²/day, removing 40–60% of the suspended solids.
In the activated sludge process the F/M ratio is 0.2–0.6 kg BOD/kg MLSS/day, the MLSS 1500–3000 mg/l for a conventional plant, the sludge age 3–15 days, and an SVI below 100 indicates a good settling sludge.
A trickling filter is a fixed-film biological reactor; the hydraulic loading is 1–4 m³/m²/day for a low-rate filter and 10–30 m³/m²/day for a high-rate filter, and recirculation improves efficiency and prevents the breeding of filter flies.
An oxidation (stabilisation) pond has a depth of 1–1.5 m, a detention time of about 2–6 weeks and a BOD loading of 200–300 kg/ha/day; oxygen is supplied symbiotically by algae and the pond works well in a warm sunny climate.
A septic tank is designed for a detention period of 12–36 hours (usually 24 h), sludge accumulation of 30–40 litres per person per year and a freeboard of 0.3–0.45 m; the effluent is disposed of through a soak pit or a drainage field.
An Imhoff tank is a two-storey tank in which sedimentation takes place in the upper compartment and sludge digestion in the lower compartment, so that the gases do not disturb the settling.
Sludge digestion has primary, secondary and tertiary stages; the digester gas contains about 65–70% methane, digestion reduces the volume and destroys pathogens, and the gas can be used as a source of energy.
Sludge disposal methods: drying beds (most common in developing countries), lagoons, incineration, composting, land application and ocean disposal.
The oxygen sag curve (Streeter-Phelps) is D = [KdL0/(Kr − Kd)](10^−Kdt − 10^−Krt) + D0 10^−Krt; the critical deficit is the maximum value of D and it occurs at the critical time tc.
Self-purification of a river occurs by dilution, sedimentation, oxidation, reduction and the action of sunlight and organisms; the sag curve passes through the zones of degradation, active decomposition, recovery and clear water.

Part 12: Irrigation, Drainage & River Training 466–50540 points

Irrigation is needed where the rainfall is inadequate or uncertain, for cash and perennial crops, to ensure a controlled water supply, and as a famine protection measure.
Types of irrigation systems: flow (perennial and inundation), lift and storage; direct flow irrigation diverts river water by a weir, while storage irrigation releases water from a reservoir.
Methods of applying water to the field: flooding (free, check, border), furrow, basin (used for paddy), sub-surface, sprinkler and drip irrigation; check (basin) flooding is common for paddy in the Terai.
Duty is expressed in hectares per cumec and is maximum at the head of the field (field duty); it decreases towards the headworks because of conveyance and other losses.
Duty depends on the type of crop, the climate, the soil, the method of irrigation and cultivation, the base period, the alignment of the canal and the efficiency of water use.
Irrigation efficiencies: conveyance (canal), application, storage and use efficiency; the overall (project) efficiency is the product of the conveyance and application efficiencies.
The kor watering is the first watering at the beginning of the crop period; typical kor depths are about 190 mm for rice and 135 mm for wheat, with kor periods of 3–4 weeks and 4 weeks respectively.
Canal classification: perennial, non-perennial, flood, navigation, power and drainage canals; in order of hierarchy the canal system consists of the main canal, branch canal, distributary, minor and watercourse.
Canal alignment: ridge (watershed) line – commands the maximum area on both sides and needs no cross-drainage works, contour line – avoids deep cutting and filling but commands only one side, and side-slope alignment.
Canal losses are seepage (percolation) and evaporation; lining the canal reduces seepage losses by about 30–40%, prevents waterlogging and weed growth and increases the carrying capacity.
Types of canal lining: cement concrete (most common and durable), brick, boulder, asphalt and plastic membrane; the choice depends on economy, availability of material and the seepage loss to be prevented.
Kennedy's theory: the critical velocity V0 = 0.55 D^0.64 (D in m) keeps the channel free of silting and scouring, and the critical velocity ratio m = V/V0 should be equal to 1 (m > 1 causes scouring and m < 1 silting).
Lacey's regime theory: silt factor f = 1.76√d, regime scour depth R = 0.47(Q/f)^1/3, velocity V = (Qf²/140)^1/6, wetted perimeter P = 4.75√Q and bed slope S = f^5/3/(3340 Q^1/6).
A channel is said to be in regime when it neither silts nor scours; Lacey's theory applies to alluvial (sandy) channels carrying fine silt in suspension.
The tractive force (shear stress) approach designs a canal on the basis of the permissible shear stress that the bed and the banks can resist without erosion; it is preferred for canals carrying coarse sediment.
Elements of a canal section: full supply level (FSL), critical depth line (CDL), berm, counter berm, freeboard, bed width and side slopes (1.5:1 to 2:1 for earthen canals in clayey soil).
Canal falls: vertical drop (Sarda type), glacis fall (ogee, trapezoidal or parabolic), straight glacis (Montague), vertical drop with a baffle platform (Inglis) and inclined drop; a glacis fall is preferred for a small drop and a Sarda fall for a larger one.
Components of diversion headworks: weir or barrage, divide wall, fish ladder, undersluices (scouring sluices), silt excluder or ejector, canal head regulator, guide bank and marginal bund.
A barrage has gates over its whole length with a low crest and gives better control of the pond level; a weir has a solid crest (with or without shutters) and the pond level varies with the discharge.
Undersluices are provided on the same side as the offtaking canal to keep the canal head clear of silt by scouring; a divide wall separates the undersluice pocket from the weir bay.
A silt excluder is located upstream of the head regulator and removes the heavier bed load through tunnels, whereas a silt ejector is located downstream of the regulator and removes silt from the canal water.
Bligh's creep theory: the seeping water creeps along the bottom of the structure and the required length of the impervious floor L = C H, where C is Bligh's coefficient (about 8–12 depending on the soil); it makes no distinction between the horizontal and the vertical creeps.
Khosla's theory (method of independent variables) uses flow nets and gives the exit gradient GE = (H/d)(1/π√λ), which must be less than the safe exit gradient of the soil (about 1/6 to 1/7 for fine sand and 1/9 to 1/10 for silt); corrections are applied for the interference of piles, the thickness of the floor and the slope of the floor.
Lane's weighted creep theory assigns a weight of 3 to the vertical creep and 1 to the horizontal creep, and is safer than Bligh's theory for the design of the impervious floor.
Energy dissipation below a weir or barrage is achieved by a stilling basin, dentated sills, impact blocks, a friction block and a dentated sill, or USBR Type I–IV basins; a hydraulic jump forms the basis of most dissipators.
Cross-drainage works: aqueduct (canal over the drainage, drainage flowing under gravity), syphon aqueduct (canal over the drainage, drainage under pressure), super passage (drainage over the canal, canal under gravity), syphon super passage (drainage over the canal, canal under pressure), level crossing and inlet and outlet.
River training works: guide banks (marginal bunds), spurs and groynes (attracting, deflecting and repelling), levees (embankments), pitching and launching aprons; they stabilise the channel and protect headworks, bridges and towns.
A guide bank confines the river to a defined channel and protects a barrage or weir from outflanking, while a launching apron protects the toe of a guide bank or spur from scour.
Watershed management measures – afforestation, contour bunding, bench terracing, check dams and gully plugging – reduce runoff, soil erosion and the sediment load reaching reservoirs and canals.
Waterlogging: the main causes are over-irrigation, seepage from canals and reservoirs, inadequate drainage and obstruction of natural drainage; the remedies are surface and subsurface drainage, lining of canals and controlled irrigation.
Surface drainage uses open field drains and deep drains, while subsurface drainage uses tile, mole and gravel drains; the spacing and depth of tile drains are determined by Hooghoudt's or Donnan's equation.
Reclamation of saline and alkali land requires subsurface drainage, leaching of salts, the application of gypsum for sodic soils and the cultivation of salt-tolerant crops.
Regulators and escapes: a canal head regulator controls the supply into a canal, a distributary head regulator controls the supply to a distributary, a cross regulator raises the water level upstream, and a canal escape (including a tail escape) discharges surplus water.
Canal outlets are non-modular (orifice and pipe), semi-modular (open flume, submerged pipe) and modular (Gibb's module, Kennedy's gauge); a modular outlet gives a constant discharge irrespective of the fluctuations in the water levels of the channel and the watercourse.
The flexibility of an outlet is the ratio of the rate of change of its discharge to the rate of change of the discharge of the distributing channel; F = 1 means proportional distribution, F > 1 hyper-proportional and F < 1 sub-proportional.
Design of a Sarda (vertical drop) fall: a trapezoidal notched crest, a baffle platform, deflector blocks and a downstream glacis; the length of the impervious floor and the depth of the downstream curtain wall are decided from the permissible exit gradient.
The capacity of a canal for a given command area is Q = AΔ/(8.64 B) cumec, where A is the area in hectares, Δ the depth of water in metres and B the base period in days.
A lined canal is designed for a higher velocity (1.5–2.5 m/s for a concrete lining) using Manning's formula, and the most economical section is obtained from the regime equations and Garrett's or Kennedy's diagrams.
Cross-drainage and regulatory structures must be provided at the crossings of canals with drainage lines; the type is selected from the relative bed levels and the discharge of the canal and the drainage.
In Nepal, command area development includes chakbandi (consolidation of plots), field channels and water user associations (WUAs), which operate and maintain tertiary canals under the Irrigation Regulation and the Water Resources Act 2049.

Part 13: Hydropower Engineering 506–54540 points

Power in kW = 9.81 Q H η, where Q is the discharge in m³/s, H the net head in metres and η the overall efficiency; 1 kWh = 3.6 MJ of energy.
The theoretical hydropower potential of Nepal is estimated at about 83,000 MW, of which roughly 42,000–45,000 MW is considered technically and economically feasible.
Hydropower plants are classified by head (low below about 30 m, medium 30–300 m, high above 300 m), by scheme (run-of-river, storage, pumped storage), by load served (base or peak) and by size (large, medium, small, mini, micro and pico).
Components of a run-of-river plant: diversion weir or barrage, intake, settling basin, head race (canal or tunnel), forebay or surge tank, penstock, powerhouse, tail race, switchyard and transmission line.
Components of a storage plant: dam, reservoir, spillway, intake, penstock, surge tank, powerhouse and tail race; the reservoir provides regulation of flow and a head that varies with the storage.
A run-of-river plant has little or no storage, so its generation follows the seasonal river flow, whereas a storage plant can store water in the wet season and meet peak demand and provide firm energy.
Load factor = average load / peak load; capacity factor = average demand / installed capacity; demand factor = maximum demand / connected load; diversity factor = sum of individual maximum demands / maximum demand on the station.
Firm energy is the energy that can be generated with a specified dependability (for example a 90% dependable flow) and the energy generated in excess of it is called secondary energy.
The installed capacity of a plant is fixed from the load duration curve, the dependable flow, the economics of storage and the peak demand; the design discharge of a run-of-river plant is often taken at a specified exceedance probability (commonly Q30 to Q40).
Types of dam: gravity, arch, buttress, homogeneous earthfill, zoned earthfill, rockfill and concrete face rockfill dam (CFRD); the selection depends on the topography, foundation geology, availability of materials and the spillway requirement.
A gravity dam resists the water pressure by its own weight and is checked for overturning (SF ≥ 1.5–2.0), sliding (SF ≥ 1.5), crushing of the masonry or concrete, tension (no tension under any combination) and shear.
Forces on a gravity dam: self-weight, water pressure (acting at H/3 above the base), uplift pressure, earthquake forces including the hydrodynamic pressure of the reservoir (Westergaard's or Zangar's formula), silt pressure, ice pressure and wave pressure.
Uplift pressure reduces the effective weight and the stability of a dam; it is reduced by a grout curtain at the upstream face, drainage galleries and relief (drainage) wells.
The elementary profile of a gravity dam is a right-angled triangle with its apex at the water surface, and the base width b = H/√(G − c), where G is the specific gravity of the masonry and c the uplift intensity factor.
Failure of dams is classified as hydraulic (overtopping, erosion of the downstream toe, wave action), structural (crushing, tension cracks, sliding) and seepage (piping, excessive uplift).
Freeboard is the vertical distance between the maximum water level and the top of the dam, provided for wave action, wind set-up and settlement; it is generally taken as 3–5% of the dam height with a minimum of about 1 m for small dams.
Types of spillway: ogee (shaped like the lower nappe of a ventilated sheet over a sharp-crested weir), chute (trough), side channel, shaft (morning glory) and siphon spillway; the ogee type is most common for concrete dams.
The discharge over an ogee spillway is Q = C L H^1.5 with C about 2.0–2.2 in SI units; the spillway must be able to pass the design flood without overtopping the dam.
Energy dissipation at the toe of a spillway: stilling basins (USBR Type I–IV), roller buckets, ski-jump (solid) buckets and dentated sills; the Froude number of the emerging jet decides the type of basin.
Types of gate: radial (Tainter), vertical lift (sluice), crest gate, roller gate, needle gate and stop-log gate; radial gates are preferred for large heads because the operating force is small.
Types of intake: run-of-river (weir with gates), tower (shaft) intake, shaft intake and canal intake; an intake is provided with trash racks, gates, air vents, bell mouths and, where needed, a silt ejector.
Trash racks prevent debris from entering the waterway; the clear spacing depends on the turbine size (about 30–100 mm for small and large machines) and the approach velocity through the rack is kept below about 1 m/s.
A settling basin removes the suspended sediment coarser than about 0.2 mm to protect the turbine; it is designed for a low flow velocity (about 0.3 m/s) and the settled material is removed periodically by flushing.
Flushing is the removal of the deposited sediment from a settling basin by opening the flushing gates at a high velocity (about 3–5 m/s); the flushing frequency is estimated from the sediment volume and the capacity of the basin.
Economic velocities: about 1.5–2 m/s in an unlined head race tunnel, 2.5–4 m/s in a lined tunnel or canal and 2–5 m/s in a penstock; higher velocities reduce the size but increase the head loss and the cost.
A tunnel lining (concrete, RCC or steel) resists the internal water pressure, the external groundwater pressure and the rock pressure; the minimum thickness of an RCC lining is generally 30–45 cm.
A surge tank reduces water hammer and provides a reflecting boundary for the pressure wave; the types are simple, restricted orifice, differential (Johnson), inclined and gallery surge tanks, and the Thoma criterion gives the minimum cross-sectional area required for stability.
Water hammer: the pressure wave velocity a = √(K/ρ)/√[1 + (K/E)(D/t)c1]; the time for a wave to travel to the reservoir and back is 2L/a, and valve closure in less than this time produces the full (direct) water hammer pressure.
A penstock conveys water from the forebay or surge tank to the turbine and is provided with anchor blocks at bends, air valves, drain valves and expansion joints; its economic diameter balances the cost of the penstock against the energy lost in friction.
Turbines are impulse (Pelton, Turgo, cross-flow) and reaction (Francis, Kaplan, propeller); the specific speed increases in the order Pelton < Francis < Kaplan.
In a Pelton wheel the jet ratio (pitch circle diameter / jet diameter) is about 12 (11–16), the bucket angle is 160–170° and the maximum efficiency is obtained when the peripheral velocity is half the jet velocity.
A Francis turbine is a mixed-flow reaction turbine with adjustable guide vanes and a draft tube, suitable for medium heads; the guide vanes regulate the discharge and the flow enters radially and leaves axially.
A Kaplan turbine is an axial-flow reaction turbine with adjustable runner blades, suitable for low head and large discharge, and it maintains a good efficiency at part load unlike a propeller turbine.
The cross-flow (Banki-Mitchell) turbine is used widely in the small and micro hydropower schemes of Nepal because it is simple, cheap, can be manufactured locally and works over a wide range of head and discharge.
Cavitation in a turbine occurs where the local pressure falls below the vapour pressure, usually at the runner outlet; Thoma's cavitation factor σ determines how far the turbine must be set below the tail race level.
The draft tube converts the kinetic energy at the turbine exit into useful pressure head; its efficiency is the ratio of the actual conversion to the velocity head at the inlet, and the common types are conical, elbow and Moody spreading.
Governing maintains a constant speed under a varying load by adjusting the discharge; mechanical (oil-pressure) and electro-hydraulic governors are used, and a flywheel smooths short-term speed fluctuations.
A pumped storage plant pumps water to the upper reservoir during off-peak hours and generates during the peak; it is used for peak shaving, frequency regulation and for absorbing surplus energy.
A multipurpose project serves irrigation, hydropower, flood control, navigation and water supply; the cost is allocated among the purposes by the alternative justified expenditure or the separable cost-remaining benefit method.
Environmental and social issues of hydropower: reservoir submergence and displacement, fish migration, sediment management, environmental (minimum) flow downstream and induced seismicity; an EIA is required for large projects under the EPR 2076.

Part 14: Transportation Engineering 546–58540 points

In Nepal the road network is classified into the strategic road network (SRN) – highways, feeder roads and district roads maintained by the Department of Roads – and the local road network (LRN) of urban and rural roads; alignment classes are plain (Terai), rolling and hilly/mountainous.
The design (ruling) speed governs the geometric design: about 80–100 km/h for a national highway in plain terrain and 50–60 km/h in hilly terrain; all elements of the alignment are designed for it.
Camber (cross slope) is provided to drain rainwater: about 2% for cement concrete and bituminous surfaces and 2.5–3% for WBM and gravel surfaces; a parabolic camber is preferred for high-speed traffic and a straight-line camber for clayey surfaces.
Carriageway width: 3.75 m for a single lane, 5.5 m for an intermediate lane, 7.0 m for two lanes without kerbs and 7.5 m for two lanes with kerbs; the right of way of a national highway is generally 30–60 m.
Stopping sight distance SSD = 0.278 Vt + V²/(254f), with V in km/h, the reaction time t = 2.5 s and the coefficient of friction f about 0.35–0.40 for a level road; overtaking sight distance OSD = d1 + d2 + d3.
Superelevation e = V²/(225R) with V in km/h and R in metres; the maximum superelevation is 7% in plain and rolling terrain and 10% in hilly and snow-bound areas.
Extra widening of the pavement on a horizontal curve = mechanical widening (off-tracking of the rear wheels) + psychological widening; a transition curve introduces the superelevation and the widening gradually.
Transition curves: spiral (clothoid, most common), cubic parabola and lemniscate; the length of the transition curve is taken as the largest of the lengths required for the rate of introduction of superelevation, of extra widening and of the centrifugal acceleration (comfort criterion).
The setback (clearance) distance for SSD on a horizontal curve is m = R[1 − cos(SSD/2R)] with the angle in radians; a larger setback is required when overtaking sight distance is to be provided.
Gradients: ruling (maximum) gradient, limiting gradient, exceptional gradient and floating gradient; grade compensation is provided on horizontal curves in hill roads to offset the loss of tractive effort.
A flexible pavement transfers the load by grain-to-grain contact through a layered structure, while a rigid pavement transfers it by slab (beam) action; flexible pavements are designed by the CBR method and rigid pavements by Westergaard's theory.
The layers of a flexible pavement from the bottom are subgrade, sub-base, base course and surface course; the design traffic is expressed in million standard axles (msa) using a standard axle load of 80 kN and a vehicle damage factor (VDF).
The equivalent single wheel load (ESWL) is the single wheel load that produces the same stress, strain or deflection as the actual dual or dual-tandem wheel assembly.
Bitumen tests: penetration (25 °C, 100 g, 5 s), ductility (27 °C, minimum 75 cm for paving grade), softening point (ring and ball), viscosity, flash and fire point, specific gravity, loss on heating and solubility in carbon disulphide.
Marshall mix design evaluates stability, flow, air voids, voids in the mineral aggregate (VMA) and voids filled with bitumen (VFB); the optimum bitumen content is the average of the contents at maximum stability, maximum bulk density and the specified air voids.
Types of bituminous construction: seal coat, surface dressing, penetration macadam, bituminous macadam (BM), dense bituminous macadam (DBM), asphalt concrete (AC) and mastic asphalt; WBM and granular sub-base are used in the lower layers.
Joints in a concrete pavement: longitudinal, construction, contraction, expansion and warping joints; dowel bars (plain round bars) transfer the load across a transverse joint and tie bars (deformed bars) hold the adjacent slabs together.
The radius of relative stiffness l = [Eh³/(12(1 − ν²)k)]^1/4; Westergaard's equations give the stresses at the interior, edge and corner of a slab under a wheel load.
Failures of flexible pavements: alligator (fatigue) cracking, rutting, corrugation, shoving, bleeding, raveling, stripping and potholes; of rigid pavements: scaling, mud pumping, corner break and joint spalling.
The fundamental relationship of traffic flow is volume = density × space mean speed (V = K × S); Greenshield's model assumes a linear relationship between speed and density, and the level of service describes the quality of the flow.
A rotary (roundabout) intersection is governed by the weaving length, the weaving angle and the proportion of weaving traffic; its capacity depends mainly on the weaving section.
Intersections are at-grade (uncontrolled, priority/stop sign controlled, signalised) or grade-separated (overpass, underpass and interchanges such as diamond, cloverleaf, trumpet and directional).
Traffic signals may be fixed-time, semi-actuated or fully actuated; Webster's formula for the optimum cycle length is C0 = (1.5L + 5)/(1 − Y), where L is the total lost time and Y the sum of the flow ratios.
Road signs are regulatory (mandatory and prohibitory), warning (cautionary) and informative (guide) signs; road markings include centre lines, edge lines, stop lines, zebra crossings and object markings.
Highway drainage comprises the camber, side drains, culverts (slab, arch, pipe, box), causeways and scuppers; the design discharge of a culvert is estimated by the rational formula from the catchment area and the rainfall intensity.
A bridge consists of the substructure (foundation, abutments, piers) and the superstructure (deck and girders); by span, structures below 6 m are culverts, 6–60 m minor bridges and above 60 m major bridges; the waterway, afflux and freeboard are decided from the HFL.
Bridge foundations: spread (open) footing, well foundation, pile foundation and caisson; the depth of the foundation is governed by the maximum scour depth, estimated by Lacey's formula R = 0.47(Q/f)^1/3.
Tunnelling methods: drill and blast (including NATM), tunnel boring machine (TBM), cut and cover and shield tunnelling; support systems are rock bolts, shotcrete, steel ribs and an RCC lining, and portals and ventilation are designed separately.
The orientation of a runway is decided by the wind rose diagram, keeping the cross-wind component within the permissible limit (about 37 km/h for large aircraft); the basic runway length is corrected for elevation, temperature, gradient and wind.
A taxiway connects the apron and hangars to the runway; a fillet is provided at the junction to facilitate turning, the exit taxiway is normally designed for a 30° turn-off angle, and the turning radius is computed from the geometry of the aircraft.
Airport pavements are flexible (asphalt) or rigid (concrete); the CBR method is used for flexible pavements and Westergaard's for rigid pavements, and the compatibility of the aircraft and the pavement is checked by the ACN/PCN method.
Railway engineering: gauges (broad 1.676 m, metre 1.0 m, narrow 0.762/0.61 m), the permanent way, sleepers, ballast, rails (52 kg and 60 kg sections), coning of wheels at 1 in 20 and creep of the rails.
Harbour works include breakwaters, quays, jetties, wharves, wet and dry docks, dredging and shore protection; the design is governed by the wave climate, the tides and the littoral drift.
A wet dock maintains a constant water level for berthing, a dry dock is used for the repair of ships, and a tidal dock has a water level that varies with the tide; an entrance lock is provided to maintain the level.
Road accidents are caused mainly by human factors (about 80%), followed by vehicle, road and environmental factors; accident studies identify black spots and the remedial engineering measures are then applied.
Highway alignment surveys: map study, reconnaissance survey, preliminary survey and final (detailed) survey including the engineering and economic surveys for the pavement design; obligatory points and geometric standards govern the alignment.
Hill road construction features: bench cutting, catch-water drains, breast and retaining walls, hairpin bends, and protection against landslides by drainage and retaining structures.
In hill roads the superelevation may be up to 10%, extra widening is greater than in the plains, and the minimum radius of the horizontal curve and the maximum gradient are governed by the terrain and the design speed.
Road maintenance: patching, crack sealing, surface dressing, overlays, recycling (hot and cold) and pavement management; riding quality is measured by the unevenness (bump integrator) index.
Parking may be on-street (parallel, 30°, 45°, 60° or 90° – parallel parking accommodates the largest number of vehicles per kerb length) or off-street; parking surveys measure accumulation, turnover, occupancy and the parking index.

Part 15: Professional Practice, Codes, Contracts & Quick Numericals 586–60015 points

The Nepal Engineering Council (NEC) was established under the Nepal Engineering Council Act, 2055 (promulgated on 2055-11-27 BS, 11 March 1999 AD) as an autonomous statutory body to regulate the engineering profession.
Registration with the NEC is mandatory to practise engineering in Nepal; the categories are General Registered Engineer, Professional Engineer and Non-Nepali Registered Engineer, and the code of conduct is prescribed by the NEC Rules, 2057.
The Nepal Engineers' Association (NEA), established in 1962 AD, is an independent non-profit professional body registered under the Social Service Act; it promotes professional development, ethics and the interests of engineers.
Public procurement in Nepal is governed by the Public Procurement Act, 2063 (2007) and the Public Procurement Regulations, 2064 (2008); the Public Procurement Monitoring Office (PPMO) is the regulatory body.
The cost estimate must be approved by the competent authority before bidding, standard norms are used for the quantities, district rates are used wherever possible, and the estimate must be consistent with the conditions of the contract documents.
Construction supervision records: site book, measurement book (MB), daily progress report, material test certificates, quality control plan, as-built drawings and the final bill with the measurement sheets.
Occupational health and safety: PPE (helmet, safety shoes, gloves, harness, goggles), safe scaffolding and ladders, shoring or benching of excavations deeper than about 1.2 m, electrical safety, first aid and the reporting of accidents are the basic requirements on a construction site.
Environmental assessment in Nepal is governed by the Environmental Protection Act, 2076 and EPR 2076; depending on the type and size of the project either an Initial Environmental Examination (IEE) or a full Environmental Impact Assessment (EIA) is required before construction, followed by monitoring reports.
Disasters are natural (earthquake, flood, landslide, fire, drought) or man-made; disaster management has four phases – mitigation, preparedness, response and recovery – and uses both structural and non-structural measures.
Nepal lies in a high seismicity zone (zones IV and V of NBC 105); ductile detailing (NBC 205 / IS 13920), a regular plan and elevation, and proper soil-foundation consideration are essential for earthquake-resistant buildings.
In Nepal the Department of Roads and the Department of Local Infrastructure (DoLI) standard specifications govern road, bridge and building works, along with the National Building Code, the NS codes and, where specified, the relevant IS codes.
Quick numericals: unit weight of a steel bar = d²/162 kg/m (d in mm); plain concrete 2400 kg/m³ and RCC 2500 kg/m³; 1 m³ of brickwork in cement mortar contains about 500 bricks; one bag of cement = 50 kg = 0.035 m³.
Conversions: 1 m³ = 35.31 cft, 1 m² = 10.76 sq ft, 1 hectare = 10,000 m², 1 ropani = 508.72 m², 1 aana = 31.79 m², 1 bigha = 6772.63 m² and 1 cft = 0.0283 m³.
Factors of safety: overturning ≥ 2.0, sliding ≥ 1.5, bearing capacity 2.5–3.0 for buildings and about 3.0 for dams; partial safety factors for material: 1.5 for concrete and 1.15 for steel.
Exam strategy: read every question twice, attempt the sure questions first, keep about one minute per question, mark and return to the difficult ones, and do not leave a question blank unless there is negative marking.

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