CE-802-B Foundation 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
   aWhat is negative skin friction? How will you calculate the negative skin friction for a single pile?
   How to answer

   • Define negative skin friction as downward drag due to settling soil
   • Explain conditions causing it - fill, consolidation, water table lowering
   • Give formula for single pile in clay: Qnf = alpha*c*As and in sand
   • Steps to locate neutral point and compute magnitude
2. 7 Marks
   bA $3 \times 3$ pile group with pile diameter and pile length of $300\text{ mm}$ and $10\text{ m}$ respectively is embedded in soft clay with cohesion of $70\text{ kN/m}^2$. The spacing between the piles (both ways) is $90\text{ cm}$ and adhesion factor is $0.6$. Calculate the capacity of the pile group. Take factor of safety $= 2.5$. Neglect end bearing.
   How to answer

   • Compute single pile skin capacity neglecting end bearing
   • Compute block failure capacity of 3x3 group
   • Take minimum of two as ultimate group capacity
   • Divide by FOS 2.5 for allowable capacity
3. 7 Marks
   aDiscuss IS Criteria for depth of bore holes in subsurface investigations.
   How to answer

   • State need for depth of exploration per IS 1892
   • Criteria based on building width, D and B, pressure bulb
   • Criteria for different structures - building, dam, embankment
   • Minimum depth and number of bore holes
4. 7 Marks
   bPlate load test was conducted on a square plate of size $0.3\text{ mm}$ in clay. The settlement observed was $4\text{ mm}$. Determine the settlement of square footing of size $2\text{ m}$ under the same load intensity.
   How to answer

   • Recall settlement relation for clay: S_footing = S_plate
   • Note size effect only for sand, not clay
   • Substitute plate settlement 4 mm
   • Conclude 4 mm settlement for 2 m footing
5. 7 Marks
   aDiscuss the modes of shear failure.
   How to answer

   • Define general, local and punching shear failure
   • Describe load-settlement curve for each mode
   • Explain role of relative density and depth
   • Sketch failure surfaces
6. 7 Marks
   bA sampling tube of $100\text{ mm}$ diameter and $2\text{ mm}$ thick. It is fitted with a cutting edge. The inside diameter of cutting edge is flushed with sampling tube. The cutting edge is $3\text{ mm}$ thick. Compute inside clearance, outside clearance, and area ratio. Comment on sample collected by tube.
   How to answer

   • Compute inside clearance from tube and cutting edge diameters
   • Compute outside clearance
   • Compute area ratio
   • Comment on sample disturbance using <10% criterion
7. 7 Marks
   aA rectangular footing $2\text{ m} \times 3\text{ m}$ carries a column load of $600\text{ kN}$ at a depth of $1\text{ m}$. The footing rests on c - soil strata, $6\text{ m}$ thick having Poisson's ratio of $0.25$ and Young's modulus of elasticity as $20000\text{ kN/m}^2$. Calculate the immediate elastic settlement of the footing. Take influence factor $= 1.06$
   How to answer

   • Compute contact pressure q = Q/(B*L)
   • Use elastic settlement formula Si = q*B*(1-nu^2)*If/Es
   • Substitute influence factor 1.06
   • Calculate settlement in mm
8. 7 Marks
   bEnlist the components of well foundation with neat sketch.
   How to answer

   • List well components - cutting edge, curb, steining, cap, etc.
   • Explain function of each component briefly
   • Draw neat labelled cross-section of well foundation
   • Mention IS provisions if relevant
9. 7 Marks
   aExplain the different components of settlement of shallow foundations. Write the equation involved in finding immediate settlement of cohesive soils.
   How to answer

   • Define total settlement = immediate + consolidation + secondary
   • Explain immediate settlement in cohesive soils
   • Give equation Si = q*B*(1-nu^2)*If/Es
   • Differentiate drained vs undrained settlement
10. 7 Marks
    bDescribe the SPT test. List the corrections used in SPT test and its need.
    How to answer

    • Describe SPT procedure - split spoon, 63.5 kg hammer, 75 cm drop
    • Explain test procedure and N-value determination
    • List corrections - overburden, dilatancy, water table
    • Explain need for each correction
11. 7 Marks
    aA square footing $2\text{ m} \times 2\text{ m}$, is founded on a depth of $1.2\text{ m}$ below the surface of a deep stratum of soft saturated clay having unit weight of $19.5\text{ kN/m}^3$. The soil has undrained parameters as $\varphi_u = 0^\circ$ and $c_u = 25\text{ kN/m}^3$ ($N_c = 5.7$, $N_q = 1$ and $N_y = 0$) and consolidated undrained parameters (triaxial test) as $\varphi' = 22.5^\circ$ and $c' = 0$ ($N_c = 21.4$, $N_q = 10.1$ and $N_y = 7.3$). Determine the ultimate bearing capacity of the foundation, (i) immediately after the construction, and (ii) few years after construction.
    How to answer

    • Compute ultimate bearing capacity using Terzaghi q_u = cNc + gamma*Df*Nq + 0.5*gamma*B*Ny
    • Use undrained parameters for (i) immediately after construction
    • Use consolidated undrained effective parameters for (ii) few years after
    • Apply shape/depth factors for square footing
12. 7 Marks
    bDifferentiate between a sheet pile and a retaining wall. List the uses of sheet piles.
    How to answer

    • Define sheet pile vs retaining wall structurally
    • Compare material, construction, load transfer
    • List uses of sheet piles - cofferdams, waterfront, etc.
    • Tabulate differences
13. 7 Marks
    aDiscuss the different methods used for boring holes. Explain CPT test.
    How to answer

    • List boring methods - auger, wash, rotary, percussion
    • Explain each method briefly with suitability
    • Describe CPT procedure and cone resistance
    • Mention advantages of CPT over SPT
14. 7 Marks
    bb) Discuss Characteristics of expansive soil and Under reamed pile:
    How to answer

    • List characteristics of expansive soil - swelling, shrinkage, mineralogy
    • Explain problems due to montmorillonite
    • Define under-reamed pile and its bulb concept
    • Mention construction and suitability in black cotton soil
15. 7 Marks
    aA masonry retaining wall is $1.5\text{ m}$ wide at top, $3.5\text{ m}$ wide at the base and $6\text{ m}$ high. It is trapezoidal in section with earth side face vertical. The backfill is level with top. The unit weight of backfill is $16\text{kN/m}^3$ for the top $3\text{ m}$ and $18\text{ kN/m}^3$ for the rest of the depth. The unit weight masonry is $23\text{ kN/m}^3$. Determine the total lateral pressure on the wall per meter run and the maximum and minimum pressure intensities at the base. Consider $\phi = 30^\circ$.
    How to answer

    • Compute Ka = (1-sin phi)/(1+sin phi) for phi=30 deg
    • Compute lateral pressure distribution for two-layer backfill
    • Compute total thrust per meter and its line of action
    • Compute eccentricity and max/min base pressure q = W/B*(1±6e/B)
16. 7 Marks
    bb) Geosynthetics:

    1. i)Explain in detail various uses of geosynthetics.
    2. ii)List various types of geosynthetics with their functions.
    How to answer

    • Explain functions - separation, reinforcement, filtration, drainage
    • List types - geotextiles, geomembranes, geogrids, geonets
    • Match each type with primary function
    • Give civil engineering applications