GPSC Civil Engineering (Combine Exam) Paper Solution (03-05-26) – Page 15

141) In a Kaplan turbine, which conditions maximise efficiency across varying flow rates?

1. Fixed guide vane angle; variable runner blade angle
2. Fixed guide vane angle; fixed runner blade angle
3. Variable guide vane angle; variable runner blade angle
4. Variable guide vane angle; fixed runner blade angle

142) Consider the following statements about the velocity distribution and boundary layer in pipe flow:

1. In fully developed laminar pipe flow, the velocity profile is parabolic and maximum velocity = 2 × average velocity.
2. In turbulent flow, the 1/7 power law gives the velocity profile: u/U = (y/R)^(1/7).
3. The viscous sublayer thickness in turbulent flow increases with increasing Reynolds number.
4. Wall shear stress in laminar flow is tw = µ(du/dy) evaluated at the wall.

Which of the above statements are correct?

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

143) Consider the following statements about the unit hydrograph theory:

1. A unit hydrograph represents 1 cm of direct runoff from a storm of specified duration over the entire watershed.
2. The time base of a unit hydrograph changes with rainfall duration.
3. Linearity assumption in unit hydrograph theory implies that ordinates of hydrograph are proportional to rainfall excess.
4. A 3-hour unit hydrograph can be derived from a 6-hour unit hydrograph using the S-curve method.

Which of the above statements are correct?

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

144) Regarding the Rational Formula (Q = CIA/360) for computing peak runoff, consider the following statements:

1. The formula assumes that rainfall intensity is uniform over the entire catchment for a duration equal to the time of concentration.
2. The runoff coefficient C can exceed 1.0 for impervious urban surfaces.
3. The rational formula is most accurate for large catchments (> 50 km²).
4. Time of concentration is the time for runoff to travel from the hydraulically most remote point to the outlet.

Which of the above statements are correct?

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

145) Which of the following correctly describes the relationship between reservoir capacity, yield and dependability?

1. For a given dependability, increasing reservoir capacity always proportionally increases yield
2. The safe yield is the maximum supply that can be guaranteed during the critical dry period
3. Secondary yield always exceeds firm yield regardless of inflow conditions
4. Mass curve analysis gives instantaneous peak discharge from a catchment

146) Consider the following statements about groundwater flow and Darcy’s Law:

1. Darcy’s Law states that the discharge velocity is proportional to the hydraulic gradient.
2. Darcy’s Law is valid for laminar flow conditions (Re based on grain size < 1 to 10).
3. Specific yield of an aquifer is always greater than specific retention.
4. A confined aquifer is one where groundwater is under pressure greater than atmospheric.

Which of the above statements are correct?

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

147) Consider the following statements about design of gravity dams using the gravity method:

1. Uplift pressure acts on the base of the dam and reduces the effective weight of the dam.
2. For no tension to develop at the heel, the resultant of all forces must lie within the middle third of the base.
3. The factor of safety against overturning is mostly calculated about the heel of the dam.
4. Piping failure in a gravity dam is prevented by providing sufficient base width, grouting, seepage control and drainage galleries.

Which of the above statements are correct?

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

148) Regarding Lacey’s regime theory for canal design, which of the following statements are correct?

1. Lacey defined regime as a condition where silt in suspension equals silt picked up by the canal.
2. Lacey’s hydraulic mean radius R = 0.47(Q/f)^(1/3), where f is Lacey’s silt factor.
3. Lacey’s theory accounts for canal shape through a wetted perimeter-discharge relationship.
4. Kennedy’s theory is superior to Lacey’s for design of channels with a wide range of sediment sizes.

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

149) Consider the following statements about the design of weirs and barrages:

1. A barrage differs from a weir in that a barrage has crest gates to control water level and discharge.
2. Bligh’s creep theory assumes that creep length is equal to the horizontal length of the foundation base.
3. Lane’s weighted creep theory assigns a weight of 1/3 to vertical creep and 1 to horizontal creep.
4. Exit gradient at the downstream end is the most critical for piping failure.

Which of the above statements are correct?

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

150) Regarding flood routing through a reservoir (level pool routing), which of the following statements is correct?

1. The peak of the outflow hydrograph exceeds the peak of the inflow hydrograph
2. The peak outflow occurs when the inflow hydrograph is on the rising limb
3. The routing process increases both the peak flow and the time to peak
4. The peak outflow occurs when inflow equals outflow, and it is always less than peak inflow