GATE Exam Questions Questions

• Time for 50% consolidation in a saturated clay layer with added drainage A saturated clay stratum drains at both the top and bottom and requires 16 years to reach 50% consolidation under load. If an additional permeable drainage layer is introduced at the mid-depth of the stratum, the time to reach 50% consolidation will be:
• Unconfined aquifer storage change — convert to hectare–metre Over an irrigable land of 50 hectares, the water table drops by 3 m. Given porosity n = 0.30 and specific retention Sr = 0.10, compute the change in storage in hectare–metres (ha–m).
• Operational uses of chlorine in wastewater treatment Chlorine is sometimes applied within activated sludge systems primarily to:
• Index properties — convert porosity to void ratio If a soil sample has porosity n = 20%, what is the corresponding void ratio e?
• Surface overflow criterion for sedimentation tank sizing A plant treats Q = 5.7 MLD. For a target to remove all particles with settling velocity v_s = 0.33 mm/s, what is the required surface area A of a rectangular sedimentation tank (ignore end effects)?
• Index properties — convert void ratio to porosity A soil has a void ratio e = 0.5. The porosity n (in %) will be approximately:
• Soil mechanics — basis of Coulomb’s earth pressure theory Coulomb’s classical theory for active and passive earth pressure on retaining walls is fundamentally based on which underlying approach?
• Structural analysis — flexibility (force) method: correct applicability Which statement best describes the appropriate use-case for the flexibility (force) method of structural analysis?
• Sewer hydraulics — minimum slope for a 2 m diameter circular sewer flowing nearly full A circular sewer of diameter 2.0 m must carry Q = 2 m^3/s when running nearly full. Assuming Manning’s n = 0.015 and using full-flow hydraulics as an approximation, what is the minimum bed slope S required to initiate this discharge?
• Water treatment — effect of pH on chlorine disinfection efficiency How does increasing pH affect the disinfection efficiency of free chlorine in conventional water treatment?
• Mechanics of materials — material property terminology A material that has identical elastic properties (moduli) in all directions at a point is termed:
• Highway design — safe overtaking sight distance at V = 100 km/h For a two-lane highway with design speed 100 km/h, estimate the safe overtaking sight distance (assume representative overtaking acceleration a ≈ 0.53 m/s^2 and standard IRC assumptions for perception and clearance). Choose the closest value.
• Surveying fundamentals — when is earth’s curvature considered? The type of land surveying in which the curvature of the Earth is explicitly taken into account is called:
• Soil mechanics – typical particle shape of clay minerals In geotechnical engineering, clay particles (e.g., kaolinite, illite, montmorillonite) are known for their characteristic morphology. Which of the following best describes the usual shape of individual clay particles?
• Highway geometric design – length–radius relation for an ideal transition curve For an ideal transition curve (clothoid/spiral), the curvature varies linearly with the curve length measured from the tangent point. What is the correct proportional relationship between the transition length l and the instantaneous radius r?
• Soil subgrade rating by Group Index (GI) A soil subgrade has Group Index GI = 7 as per the group index method. Based on standard GI classifications for highway subgrades, how should this soil be rated?
• Rigid pavements – expansion joint spacing from thermal movement A cement concrete pavement uses expansion joints with a joint gap width of 2.5 cm. For a maximum rise in slab temperature of 25 °C and a coefficient of thermal expansion for concrete α = 10 × 10^-6 per °C, determine the appropriate spacing between expansion joints (in metres).
• Fluid mechanics – isotropy of pressure at a point If, for a fluid in motion, the pressure measured at a point is the same in all directions (i.e., normal stresses are equal in every orientation), the fluid can be idealized as which of the following?
• Ground improvement – primary purpose of sand drains (vertical drains) In soft, saturated clay deposits, sand drains (now often prefabricated vertical drains) are installed primarily to achieve which outcome?
• Pavement engineering – unit of the coefficient of subgrade modulus (k) The coefficient of subgrade modulus k (modulus of subgrade reaction) is defined as the pressure per unit surface deflection for a plate/area on subgrade. What is its correct SI unit?