CE-802-B Foundation Engineering - May 2022 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 do you understand by significant depth of soil exploration? List out the various methods of site exploration.
   How to answer

   • Define significant depth / depth of influence for soil exploration
   • Factors governing depth: type of structure, load intensity, soil variability
   • List methods of site exploration: open pits, borings, soundings, geophysical methods
2. 7 Marks
   bDefine Floating Foundation. Explain proportioning of Raft foundations.
   How to answer

   • Define floating foundation: weight of excavated soil equals building load
   • Principle of proportioning raft for uniform settlement
   • Steps for sizing, thickness and reinforcement of raft
3. 7 Marks
   aDifferentiate between SPT and SCPT.
   How to answer

   • Define SPT: dynamic penetration, split-spoon, N-value
   • Define SCPT: static cone penetration, cone resistance and friction
   • Tabular differences: procedure, measurements, applicability
4. 7 Marks
   bGive BIS method for calculating bearing capacity of foundation.
   How to answer

   • State BIS code IS:6403 assumptions for bearing capacity
   • Give bearing capacity factors and shape/depth/inclination factors
   • Write final equation for ultimate and safe bearing capacity
5. 7 Marks
   aWhat is static load carrying Capacity of Pile? Give its expression also.
   How to answer

   • Define static pile capacity as sum of skin friction and end bearing
   • Explain components for driven/bored piles in cohesionless/cohesive soils
   • Write static formula $Q_u = Q_b + Q_s$ with expressions
6. 7 Marks
   bA rectangular footing $2\,m \times 3\,m$ carries a column load of $600\,kN$ at a depth of $1\,m$. The footing rests on a $c - \phi$ soil strata $6\,m$ thick, having poisson's ratio of $0.25$ and Young's modulus of elasticity as $20{,}000\,kN/m^2$. Calculate the immediate elastic settlement of the footing.
   How to answer

   • Compute contact pressure $q = Q/(B\times L)$ at depth
   • Use elastic settlement formula $S_i = qB(1-\mu^2)I/E_s$
   • Substitute $B=2\,m, L=3\,m, \mu=0.25, E_s=20000\,kN/m^2$ and influence factor to get $S_i$
7. 7 Marks
   aWrite short note on bore-log report with neat sketch.
   How to answer

   • Define bore-log: record of strata vs depth from boring
   • List contents: soil description, SPT, water table, samples
   • Draw neat labelled bore-log sketch
8. 7 Marks
   bGive comparison of Rankine's and Coulomb's theory.
   How to answer

   • State assumptions of Rankine vs Coulomb theories
   • Compare wall friction, failure surface, backfill conditions
   • Summarize applicability and limitations in table
9. 7 Marks
   aDefine Pile Foundation. Discuss about the types of pile and their functions.
   How to answer

   • Define pile foundation: deep foundation transferring load to deeper strata
   • Classify piles by material, installation and load transfer
   • State functions: bearing, friction, compaction, anchor, fender
10. 7 Marks
    bDerive Boussinesq equation for a point load.
    How to answer

    • State Boussinesq assumptions for elastic half-space under point load
    • Consider equilibrium of stresses on horizontal plane
    • Derive vertical stress $\sigma_z = 3Qz^3/(2\pi R^5) = QB/z^2$
11. 7 Marks
    aWhat are the different methods of soil stabilization? Explain with neat sketches.
    How to answer

    • Define soil stabilization and its objectives
    • List methods: mechanical, cement, lime, bituminous, chemical, grouting
    • Explain each with neat sketches
12. 7 Marks
    bCompute the intensities of active and passive earth pressure at depth of $10\,m$ in dry cohesion less sand with an angle of internal friction of $30^\circ$ and unit weight of $18\,kN/m^3$. What will be the intensities of active and passive earth pressure if the water level rises to the ground level? Take saturated unit weight of sand as $22\,kN/m^3$.
    How to answer

    • Compute $K_a=(1-\sin\phi)/(1+\sin\phi)$ and $K_p=1/K_a$ for $\phi=30^\circ$
    • Calculate $p_a=K_a\gamma H$ and $p_p=K_p\gamma H$ for dry case $H=10\,m$
    • Recompute with submerged unit weight plus hydrostatic pressure when water rises to GL
13. 7 Marks
    aDefine Safe Bearing Capacity. List down effects of negative skin friction. https://www.rgpvonline.com
    How to answer

    • Define safe bearing capacity: ultimate/net safe with factor of safety
    • Define negative skin friction: drag on pile due to settling soil
    • List effects: increased pile load, settlement, reduced capacity
14. 7 Marks
    bDetermine the stresses at the top and bottom of a vertical cut, $5.5m$ deep in soil with $\phi' = 15^\circ$ and $c' = 0.92\,t/m^3$ $(19.2\,kN/m^2)$ and $\gamma = 1.85\,t/m^3$. What could be the depth of the potential crack? What is the maximum depth of excavation that can be left unsupported.
    How to answer

    • Use $p_a = \gamma z K_a -2c'\sqrt{K_a}$ with $K_a$ for $\phi'=15^\circ$
    • Evaluate stresses at $z=0$ and $z=5.5\,m$; find tension crack depth $z_0=2c'/(\gamma\sqrt{K_a})$
    • Compute critical unsupported depth $H_c=2z_0 = 4c'/(\gamma\sqrt{K_a})$
15. 7 Marks
    aDiscuss essential difference between Boussinesq's and Westergaard's theories.
    How to answer

    • State Boussinesq assumptions: homogeneous isotropic elastic half-space
    • State Westergaard assumptions: stratified with thin rigid layers preventing lateral strain
    • Compare stress distribution factors and magnitude of vertical stress
16. 7 Marks
    bExplain in detail the rotary drilling technique. State also its advantages over other methods of boring.
    How to answer

    • Describe rotary drilling: rotating bit, drilling fluid circulation, casing
    • Explain procedure and equipment components
    • List advantages: speed, depth, sampling in all soils/rocks over other boring methods