GATE Exam Questions Questions

• Wastewater analysis – compute BOD5 from diluted bottle data In a 5-day BOD test at 20 °C, a 5% dilution is used (15 mL sample + 285 mL dilution water in a 300 mL bottle). After incubation, the DO of the sample bottle is 3.80 mg/L and the DO of the dilution-water blank bottle is 8.80 mg/L. The dissolved oxygen originally present in the undiluted sample is 0.80 mg/L. Determine the BOD5 of the sample (mg/L).
• Pavement design traffic – cumulative standard axles for divided highway An existing 2-lane NH section is to be widened and strengthened as a divided highway. Current traffic in one direction is 2500 commercial vehicles (CV) per day. Construction duration is 1 year. Design CBR of subgrade = 5%. Given: annual traffic growth rate for CV = 8%, vehicle damage factor (VDF) = 3.5 standard axles per CV, design life = 10 years, and traffic distribution factor = 0.75. Compute the cumulative standard axles (msa) for design.
• Hardy Cross Principles for Pipe Networks In the analysis of a closed network of pipes (e.g., using Hardy Cross or equivalent methods), which of the following statements is fundamentally correct about the energy balance around a loop and continuity at junctions?
• Water Treatment Coagulation – Effect of Alum (Al2(SO4)3) on pH When aluminum sulfate (alum) is used as a coagulant in conventional water treatment, what is its typical effect on the pH of the treated water (assuming normal alkalinity and no external pH control)?
• Serviceability Limit – Deflection Criterion for Gantry Girders with EOT Crane For a gantry girder of span 6 m carrying an Electric Overhead Travelling (EOT) crane of 200 kN capacity, what is the maximum permissible vertical deflection under service load as per typical gantry-girder limits?
• Shear–Moment Relationship in Beams If the shear force V at a section of a beam is zero, what can be stated about the bending moment M at that same section?
• Stress Distribution by Load Dispersion – Average Stress Beneath a Footing A 2 m × 1 m footing applies a uniform contact pressure of 150 kN/m² to the soil surface. Assuming a load dispersion of 2 vertical to 1 horizontal in soil, what is the average vertical stress at a depth of 1.0 m beneath the footing?
• Why Bitumen for Highways? – Key Material Properties Bituminous binders are extensively used in highway construction primarily because of which pair of material properties?
• Transition Curve Length from Rate of Gain of Radial Acceleration A horizontal circular curve has deflection angle 55° and radius R = 250 m. Provide a transition curve at each end such that the rate of gain of radial acceleration C is 0.3 m/s^3 at design speed v = 50 km/h. What is the required transition length L (per end)?
• Soil Classification (USCS) – Symbols for Silty Sand and Clayey Sand Under the Unified Soil Classification System (USCS), which pair of group symbols corresponds to silty sand and clayey sand, respectively?
• Rainfall Representation – Definition of a Hyetograph In hydrology, a hyetograph is a plot representing which rainfall variable as a function of time?
• Fluid Mechanics – Cause of cavitation in hydraulic machines and flow systems Identify the primary condition that leads to cavitation formation in liquids (e.g., in pumps, turbines, and propeller flows).
• Groundwater – Interference of two fully penetrating wells in a confined aquifer (Thiem superposition) Two identical, fully penetrating wells are L metres apart in a homogeneous confined aquifer. At the midpoint (0.5L from each well), the drawdown is 2.0 m when only Well 1 is pumped at Q1 m^3/s. When both wells are pumped at identical steady rates Q2 m^3/s, the drawdown at the midpoint becomes 8.0 m. The drawdown at each well during pumping remains 10.0 m, and the radius of influence exceeds 0.5L. Determine Q1/Q2.
• Foundation Engineering – Plate load test extrapolation on sand A 30 cm × 30 cm test plate on sand settles 10 mm at a given pressure. Estimate the settlement of a 150 cm × 200 cm footing on the same sand under the same pressure.
• Open-Channel Design – “Best” (most economical) trapezoidal section For a given area and given side slopes (m:1, horizontal:vertical), which statement is characteristic of the most economical trapezoidal channel section?
• Open-Channel Flow – Critical depth criterion Critical depth occurs in an open channel under which of the following conditions?
• Water Quality – Temporary hardness of water Temporary hardness arises primarily due to the presence of which dissolved salts?
• Soil Dynamics – Soils most susceptible to liquefaction during seismic shaking Identify the soil type that is most vulnerable to liquefaction.
• Unconfined Aquifer – Specific yield from pumped volume and water-table decline From an area of 5 km^2, a total of 3.0 × 10^6 m^3 of groundwater is pumped uniformly from an unconfined aquifer, lowering the water table from 102 m to 99 m. Compute the specific yield (dimensionless).
• Lateral buckling of a discretely braced I-beam — parameter sensitivity For a symmetrical I-section beam with discrete lateral supports (i.e., the compression flange is laterally braced at intervals), the maximum allowable compressive stress corresponding to lateral–torsional buckling depends on several section and bracing properties. Which one of the following does it NOT depend upon?