GPSC Civil Engineering (Combine Exam) Paper Solution (03-05-26) – Page 5

41) In ‘Roof Construction’, which of the following statements is incorrect?

1. The ‘King Post Truss’ is suitable for spans up to 8 m; it has a central vertical member (king post) carrying the tie beam.
2. The ‘King Post Truss’ is suitable for spans of 8-12 m and has two vertical posts allowing an open space in the middle.
3. The pitch of a roof (ratio of rise to span) must not be less than 1/4 for corrugated GI sheet roofing to ensure adequate drainage.
4. ‘Purlins’ run parallel to the ridge and perpendicular to the principal rafters, providing intermediate support to the common rafters and sheets.

42) ‘Dampness in Buildings’ can occur through various mechanisms. Which of the following methods of preventing dampness and their applications are INCORRECTLY matched?

1. Damp Proof Course (DPC) using bituminous felt (Type A/B of IS 1322) – prevents rising dampness in walls at plinth level.
2. Cavity walls – prevent driving rain penetration to the inner leaf.
3. Integral waterproofing compounds in concrete – cannot prevent moisture penetration in water-retaining structures and basements.
4. Membrane waterproofing with APP/SBS modified bitumen on roof – prevents ingress from precipitation.

43) In ‘Cofferdams’ used for underwater/below groundwater table construction, which of the following is incorrectly stated?

1. A single-wall cofferdam consists of sheet piles driven around the excavation area; it is suitable for shallow water depths up to 4-6 m.
2. A double-wall cofferdam consists of two parallel rows of sheet piles with granular fill between them; it can resist higher hydrostatic pressures for deeper water.
3. Cellular cofferdams (using interlocking sheet piles in circular cells) are self-supporting and not suitable for very deep water (15-30 m) and large plan areas.
4. Rock-fill cofferdams (earth-rock bunds) are constructed upstream and downstream of dam sites; they are the most economical type for major river diversion works.

44) Two small orifices (A) and (B) of diameters 1 cm and 2 cm respectively are placed on the sides of the tank at depths (h₁) and (h₂) below the open liquid surface. If discharges through (A) and (B) are equal, then ratio of (h₁) and (h₂) (assuming coefficient of discharge (Cd) to be the same for both the orifices) will be

1. 16:1
2. 8:1
3. 4:1
4. 2:1

45) Which of the following incorrectly describes ‘Well Point Dewatering’?

1. Well points are small diameter pipes with perforated tips driven into the ground at close spacing, connected to a header pipe and vacuum pump.
2. Well point dewatering lowers the groundwater table by suction; the maximum theoretical lift of a single-stage well point system is approximately 6-7 m.
3. The spacing of well points typically ranges from 1 to 3 m and they are installed at 1-1.5 m outside the excavation limit.
4. For excavations requiring water table lowering > 10 m, single-stage well point systems must be used.

46) In ‘Orientation of Buildings’ for energy efficiency in Indian climatic conditions, which of the following principles is incorrectly stated?

1. For residential buildings in India (tropical climate), the longer axis of the building should be oriented along the East-West direction to minimise sun exposure on long facades.
2. The South-facing wall receives maximum solar radiation in Indian conditions during summer months (contrary to North hemisphere expectation).
3. Chajjas (horizontal projections) over South-facing windows effectively block high-angle summer sun while allowing low-angle winter sun for passive solar heating.
4. Cross-ventilation is maximized when buildings are oriented with the longer axis perpendicular to the prevailing wind direction.

47) For ‘Floors’ construction in industrial buildings, which of the following types and their characteristics is INCORRECTLY matched?

1. Granolithic Floor – made with 1:1:2 cement: granite chips: sand mix; provides very soft, less abrasion-resistant surface for industrial use.
2. ‘Trowel-finished Concrete Floor’ with hardener (metallic or non-metallic) – hardener applied while concrete is green, increases surface hardness by 2-3 × compared to plain concrete.
3. ‘Epoxy Flooring’ (self-levelling, 3-5 mm thick) – used in pharmaceutical, food processing plants; provides chemical resistance, seamless hygiene surface.
4. ‘Kota Stone Flooring’ – natural limestone quarried in Kota, Rajasthan; used widely in institutional buildings for durability and low maintenance.

48) In the construction of ‘Stairs’, the following rules apply as per NBC 2016 and IS 456:2000:

1. The riser (R) and tread (T) relationship: 2R + T = 600 mm to 640 mm (or alternatively R + T = 450 mm to 470 mm).
2. Minimum tread width for public buildings = 300 mm; minimum tread width for residential buildings = 250 mm.
3. The minimum riser height for residential staircases as per NBC 2016 = 290 mm.
4. A landing shall not be less than the width of the stair flight.

Which of the above statements are correct?

1. 1 and 3 only
2. 1, 2 and 3 only
3. 2, 3 and 4 only
4. 1, 2 and 4 only

49) The velocity potential function in a two dimensional flow field is given by φ = x² – y² The magnitude of velocity at point (2, 1) is

1. √(26)
2. √(20)
3. √(30)
4. √(22)

50) In the design and construction of ‘Retaining Walls’ for building foundations and site development, which failure modes and their corresponding design checks is incorrectly described?

1. Overturning failure – resisting moment (gravity) vs overturning moment (soil pressure); FOS ≥ 1.5.
2. Bearing capacity failure – maximum soil pressure at toe must exceed the safe bearing capacity (SBC) of foundation soil.
3. Sliding failure – friction at base + passive resistance vs active earth pressure; FOS ≥ 1.5.
4. Deep-seated circular failure (slope stability) – relevant for tall retaining walls on soft soils; checked by Swedish slip circle or Spencer method.