CE-701 Geotechnical Engineering - Jun 2025 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 7 Marks
   aTwo point loads P and Q act on the ground surface 8m apart. The magnitude of P is 100kN and that of Q is 80kN. Point A is at a depth of 6m directly below P and point B is at a depth of 5m directly below Q. Point C is between P and Q and it is at a distance of 4m from P. Point C lies at a depth of 3m below the ground surface. Calculate the increase in vertical stresses at A, B and C due to the point loads.
   How to answer

   • State Boussinesq vertical stress formula for point load
   • Compute influence factors for direct and offset loads
   • Superpose contributions of P and Q at A, B and C
   • Report increased vertical stresses at A, B, C
2. 7 Marks
   bExplain determination of coefficient of permeability by constant head method.
   How to answer

   • Define coefficient of permeability
   • Describe constant head permeameter setup
   • State Darcy law formula $k = QL/(Aht)$
   • List procedure and applicability to coarse soils
3. 7 Marks
   aThere is a layer of soft clay 4 m thick under a newly constructed building. The overburden pressure over the center of the clay layer is 300 kN/m2. Compute the settlement, if there is an increase in pressure due to construction of 100 kN/m2. Take $C_c = 0.50$, $G = 2.70$. The water content of the deposit was found to be 50 %.
   How to answer

   • Compute initial void ratio from $wG = Se$ for saturated clay
   • State consolidation settlement formula $s_c = H_0 C_c/(1+e_0) \log[(\sigma_0+\Delta\sigma)/\sigma_0]$
   • Substitute $H_0, C_c, G, w, \sigma_0, \Delta\sigma$
   • Calculate settlement value
4. 7 Marks
   bExplain any one method to compute the coefficient of consolidation.
   How to answer

   • Define coefficient of consolidation $c_v$
   • Describe Casagrande log-time or Taylor root-time method
   • Explain plotting and determination of $t_{50}$ or $t_{90}$
   • Give formula $c_v = T_v d^2/t$
5. 6 Marks
   aDefine Quick sand condition and Derive the expression for critical hydraulic gradient.
   How to answer

   • Define quick sand condition with effective stress zero
   • Consider upward seepage forces on soil prism
   • Equate seepage force to submerged weight
   • Derive $i_c = (G-1)/(1+e)$
6. 8 Marks
   bA soil strata consists of 3 layers of thickness 1 m, 1.5 m and 1.9 m having the coefficients of permeability of $2.3 \times 10^{-3}$ cm/s, $1.85 \times 10^{-3}$ cm/s and $3.5 \times 10^{-4}$ cm/s respectively. Estimate the average coefficient of permeability in the direction:

   1. i)parallel and
   2. ii)normal to the flow
   How to answer

   • List layer thicknesses and $k_1,k_2,k_3$
   • Apply weighted arithmetic mean for flow parallel to bedding
   • Apply harmonic mean for flow normal to bedding
   • Compute $k_H$ and $k_V$ values
7. 7 Marks
   aThe following values of sand are given: $D_{60} = 0.77$ mm, $D_{30} = 0.41$mm and $D_{10} = 0.30$ mm. Determine, $C_u$ and $C_c$ and state if it is a well graded or poorly graded soil?
   How to answer

   • Compute $C_u = D_{60}/D_{10}$ and $C_c = D_{30}^2/(D_{60}D_{10})$
   • Substitute $D_{60}, D_{30}, D_{10}$ values
   • State criteria for well graded sand
   • Classify as well or poorly graded
8. 7 Marks
   bWhat are the various drainage conditions and what is the significance of each drainage conditions?
   How to answer

   • Define UU, CU, CD drainage conditions
   • Explain pore pressure and volume change in each
   • State significance for stability and construction rate
   • Give examples of application
9. 7 Marks
   aThe moist unit weight of a soil is 16.50 kN/m3 Given that the water content = 15% and specific gravity of soil solids = 2.70, find the dry unit weight, porosity, degree of saturation the mass of water that must be added to reach full saturation.
   How to answer

   • Compute dry unit weight from $\gamma_d = \gamma/(1+w)$
   • Find void ratio, porosity and degree of saturation using $G, w$
   • Compute water needed for $S=100\%$
   • Report $\gamma_d, n, S$ and added water mass
10. 7 Marks
    bDerive the expression to determine the average coefficient of permeability in the horizontal direction for a stratified soil deposit.
    How to answer

    • Assume horizontal flow with same hydraulic gradient
    • Equate total discharge to sum of layer discharges
    • Derive $k_H = \sum k_i H_i / H$
    • State assumptions for stratified deposit
11. 7 Marks
    aExplain the difference between IS light and heavy compactions?
    How to answer

    • State energy, layers and blows for IS light test
    • State energy, layers and blows for IS heavy test
    • Compare mould, hammer weight and drop
    • Summarize effect on MDD and OMC
12. 7 Marks
    bShow IS soil classification based on grain size? Explain Total, neutral and effective stresses?
    How to answer

    • Show IS classification based on grain size fractions
    • Define gravel, sand, silt and clay limits
    • Define total, neutral and effective stress
    • Give relation $\sigma' = \sigma - u$
13. 7 Marks
    aHow do soils attain their shear strength? Explain soil strength Envelope?
    How to answer

    • Explain cohesion and friction components
    • Describe Mohr-Coulomb failure criterion
    • Define strength envelope with c and phi
    • Sketch envelope diagram
14. 7 Marks
    bWhat are the methods of soil stabilization? Explain functions and applications of geo synthetic in detail.
    How to answer

    • List mechanical, chemical and geosynthetic stabilization
    • Explain functions: separation, reinforcement, filtration
    • Describe applications of geotextiles and geogrids
    • Give examples of field use
15. 7 Marks
    aCompare and contrast Boussinesq's and Westergaard's theories?
    How to answer

    • State assumptions of Boussinesq isotropic theory
    • State assumptions of Westergaard anisotropic theory
    • Compare stress distribution factors
    • Summarize differences in applicability
16. 7 Marks
    bExplain the three standard triaxial shear tests with respect to drainage conditions?
    How to answer

    • Define UU, CU and CD triaxial tests
    • Explain drainage valves open/closed in each stage
    • State pore pressure and volume change measurement
    • Mention Mohr envelopes for each test