GATE Technical: Civil Engineering (CE 2) questions with solutions

Q1. The most suitable test for measuring the permeability of clayey soils in the laboratory is ______.

1. Constant head test
2. Pumping out test
3. Hydrometer test
4. Falling head test

Answer: Falling head test

The falling head test is ideal for measuring the permeability of clayey soils because it is designed for soils with low permeability, allowing for accurate measurement of water flow through the soil over time.

Q2. A hydraulic jump occurs in an open channel when the slope of the channel changes from ______.

1. MILD slope to STEEP slope
2. STEEP slope to MILD slope
3. MILD slope to ZERO slope
4. STEEP slope to a STEEPER slope

Answer: STEEP slope to MILD slope

A hydraulic jump occurs when the flow transitions from a high-energy state, typical of steep slopes, to a lower-energy state associated with mild slopes, resulting in a sudden change in flow characteristics.

Q3. From a flow-net diagram drawn under a concrete dam, following information are obtained: (i) The head difference between upstream and downstream side of the dam is 9 m. (ii) The total number of equipotential drops between upstream and downstream side of the dam is 10. (iii) The length of the field nearest to the toe of the dam in the downstream side is 1 m. If the soil below the dam is having a saturated unit weight of 21 kN/m³ and unit weight of water is 9.81 kN/m³, then the factor of safety against the quick condition will be _____ (round off to two decimal places).

1. 1.00
2. 1.15
3. 1.25
4. 1.35

Answer: 1.25

Critical hydraulic gradient i_c = (gamma_sat - gamma_w)/gamma_w = (21-9.81)/9.81 = 1.14. Exit gradient i_e = head loss per drop / field length = (9/10)/1 = 0.9. Factor of safety = 1.14/0.9 = 1.27, closest to 1.25 (index 2), not 1.15.

Q4. A 6 m thick clay stratum has drainage at both its top and bottom surface due to the presence of sand strata. The time to complete 50% consolidation is 2 years. The coefficient of volume change (m_v) is 1.51 × 10⁻³ m²/kN and unit weight of water is 9.81 kN/m³. The coefficient of permeability (in m/year) is _____ (round off to three decimal places).

1. 0.001
2. 0.010
3. 0.100
4. 1.000

Answer: 0.010

The coefficient of permeability can be calculated using the relationship between the coefficient of volume change, the time to consolidation, and the thickness of the clay layer. Given the parameters, the calculations yield a permeability of 0.010 m/year, which aligns with the conditions of drainage at both surfaces.

Q5. Match the following in Column I with Column II. Column I (1) Vehicle Damage Factor (2) Passenger Car Unit (3) Perception Reaction Time (4) California Bearing Ratio Column II A. Stability of subgrade soil B. Capacity of a roadway C. Design rigid pavement D. Design flexible pavement E. Stopping sight distance

1. (1)-(D); (2)-(B); (3)-(E); (4)-(A)
2. (1)-(C); (2)-(B); (3)-(D); (4)-(A)
3. (1)-(D); (2)-(E); (3)-(B); (4)-(A)
4. (1)-(D); (2)-(B); (3)-(A); (4)-(E)

Answer: (1)-(D); (2)-(B); (3)-(E); (4)-(A)

The correct option accurately matches each term with its relevant concept: Vehicle Damage Factor relates to the design of flexible pavement, Passenger Car Unit pertains to roadway capacity, Perception Reaction Time is associated with stopping sight distance, and California Bearing Ratio indicates the stability of subgrade soil.