GATE Technical: GATE 2016 Civil Engineering Set-1 questions with solutions

Q1. In shear design of an RC beam, other than the allowable shear strength of concrete (τ_c), there is also an additional check suggested in IS 456-2000 with respect to the maximum permissible shear stress (τ_cmax). The check for τ_cmax is required to take care of

1. additional shear resistance from reinforcement
2. additional shear stress that comes from accidental loading
3. possibility of failure of concrete by diagonal tension
4. possibility of crushing of concrete by diagonal compression

Answer: possibility of crushing of concrete by diagonal compression

The check for maximum permissible shear stress (τ_cmax) is necessary to ensure that the concrete does not fail due to diagonal compression, which can occur under high shear forces. This consideration helps prevent structural failure by ensuring that the concrete can withstand the compressive stresses that develop in the diagonal planes of the beam.

Q2. Bull's trench kiln is used in the manufacturing of

1. lime
2. cement
3. bricks
4. none of these

Answer: bricks

Bull's trench kiln is specifically designed for the efficient production of bricks, allowing for continuous firing and improved energy efficiency in the brick-making process.

Q3. The compound which is largely responsible for initial setting and early strength gain of Ordinary Portland Cement is

1. C3A
2. C3S
3. C2S
4. C4AF

Answer: C3S

C3S, or tricalcium silicate, is the primary compound in Ordinary Portland Cement that contributes to the initial setting and early strength gain due to its rapid hydration properties.

Q4. In the consolidated undrained triaxial test on a saturated soil sample, the pore water pressure is zero

1. during shearing stage only
2. at the end of consolidation stage only
3. both at the end of consolidation and during shearing stages
4. under none of the above conditions

Answer: at the end of consolidation stage only

In a consolidated undrained triaxial test, the pore water pressure is zero at the end of the consolidation stage because the soil has fully consolidated and excess pore water pressure has dissipated, allowing the effective stress to be fully mobilized before shearing begins.

Q5. A fine grained soil is found to be plastic in the water content range of 26-48%. As per Indian Standard Classification System, the soil is classified as

1. CL
2. CH
3. CL-ML
4. CI

Answer: CI

The soil is plastic from 26% to 48% water content, so the liquid limit is 48%. Since 35% < LL < 50%, the IS classification is CI (clay of intermediate plasticity), not CH (which requires LL > 50%).

Q6. A vertical cut is to be made in a soil mass having cohesion c, angle of internal friction φ, and unit weight γ. Considering Kₐ and Kₚ as the coefficients of active and passive earth pressures, respectively, the maximum depth of unsupported excavation is

1. 4c/(γ√Kₚ)
2. 2c√Kₚ/γ
3. 4c√Kₐ/γ
4. 4c/(γ√Kₐ)

Answer: 4c/(γ√Kₐ)

The correct option is derived from the relationship between soil cohesion, unit weight, and the coefficients of earth pressure. The formula 4c/(γ√Kₐ) reflects the maximum depth of unsupported excavation, taking into account the active earth pressure conditions that allow for greater stability in the excavation.

Q7. The type of flood routing (Group I) and the equation(s) used for the purpose (Group II) are given below. Group I P Hydrologic flood routing Q Hydraulic flood routing Group II 1. Continuity equation 2. Momentum equation 3. Energy equation The correct match is

1. P - 1; Q - 1, 2 & 3
2. P - 1; Q - 1 & 2 only
3. P - 1 & 2; Q - 1 only
4. P - 1 & 2; Q - 1 & 2

Answer: P - 1; Q - 1 & 2 only

Hydrologic flood routing primarily relies on the continuity equation to analyze the flow of water through a watershed, while hydraulic flood routing utilizes both the continuity and momentum equations to describe the flow in open channels, making option B the correct match.

Q8. Pre-cursors to photochemical oxidants are

1. NOx, VOCs and sunlight
2. SO2, CO2 and sunlight
3. H2S, CO and sunlight
4. SO2, NH3 and sunlight

Answer: NOx, VOCs and sunlight

Photochemical oxidants are formed when nitrogen oxides (NOx) and volatile organic compounds (VOCs) react in the presence of sunlight, leading to the creation of harmful pollutants like ozone.

Q9. Crown corrosion in a reinforced concrete sewer is caused by:

1. H2S
2. CO2
3. CH4
4. NH3

Answer: H2S

H2S, or hydrogen sulfide, is a corrosive gas that can form in sewer systems, particularly in the presence of organic matter and anaerobic conditions, leading to the deterioration of concrete through a process known as crown corrosion.

Q10. Match the items in Group - I with those in Group - II and choose the right combination. Group - I P. Activated sludge process Q. Rising of sludge R. Conventional nitrification S. Biological nitrogen removal Group - II 1. Nitrifiers and denitrifiers 2. Autotrophic bacteria 3. Heterotrophic bacteria 4. Denitrifiers

1. P-3, Q-4, R-2, S-1
2. P-2, Q-3, R-4, S-1
3. P-3, Q-2, R-4, S-1
4. P-1, Q-4, R-2, S-3

Answer: P-3, Q-4, R-2, S-1

The activated sludge process primarily involves heterotrophic bacteria (P-3) that break down organic matter. Rising of sludge is associated with denitrifiers (Q-4) that help in nitrogen removal. Conventional nitrification is carried out by autotrophic bacteria (R-2), while biological nitrogen removal involves both nitrifiers and denitrifiers (S-1) working together.

Q11. The minimum number of satellites needed for a GPS to determine its position precisely is

1. 2
2. 3
3. 4
4. 24

Answer: 4

To accurately determine a position in three-dimensional space, a GPS receiver requires signals from at least four satellites. This allows it to calculate latitude, longitude, and altitude, as well as to account for timing discrepancies.

Q12. The system that uses the Sun as a source of electromagnetic energy and records the naturally radiated and reflected energy from the objects is called

1. Geographical Information System
2. Global Positioning System
3. Passive Remote Sensing
4. Active Remote Sensing

Answer: Passive Remote Sensing

Passive Remote Sensing relies on the natural energy emitted or reflected by objects, primarily from the Sun, to gather data, making it distinct from Active Remote Sensing, which uses its own energy source.

Q13. A reinforced concrete (RC) beam with width of 250 mm and effective depth of 400 mm is reinforced with Fe415 steel. As per the provisions of IS 456-2000, the minimum and maximum amount of tensile reinforcement (expressed in mm²) for the section are, respectively

1. 250 and 3500
2. 205 and 4000
3. 270 and 2000
4. 300 and 2500

Answer: 205 and 4000

The correct option provides the minimum and maximum tensile reinforcement values as per IS 456-2000 guidelines, which specify that the minimum area of steel should be based on the width and effective depth of the beam, while the maximum area is determined to ensure proper ductility and prevent failure.

Q14. A propped cantilever of span L carries a vertical concentrated load at the mid-span. If the plastic moment capacity of the section is Mₚ, the magnitude of the collapse load is

1. 8Mₚ/L
2. 6Mₚ/L
3. 4Mₚ/L
4. 2Mₚ/L

Answer: 6Mₚ/L

The collapse load for a propped cantilever under a mid-span concentrated load can be determined using plastic analysis, which shows that the structure can sustain a maximum load of 6 times the plastic moment capacity divided by the span length, reflecting the balance of moments and the formation of plastic hinges.

Q15. A 4 m wide rectangular channel, having bed slope of 0.001 carries a discharge of 16 m³/s. Considering Manning's roughness coefficient = 0.012 and g = 10 m/s², the category of the channel slope is

1. horizontal
2. mild
3. critical
4. step

Answer: mild

A channel is classified as mild when its slope is less than the critical slope but greater than zero, allowing for a smooth flow regime. Given the bed slope of 0.001 and the discharge, the channel does not meet the criteria for horizontal or critical slopes, thus categorizing it as mild.