CE-802-B Foundation Engineering - May 2023 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 are various types of footing? Mention the basic criteria for satisfactory performance of a foundation.
   How to answer

   • List isolated, combined, strip, mat/raft, etc. footings
   • Criteria: shear failure safety, settlement within permissible limits
   • Criteria: location of water table, eccentricity, durability
2. 7 Marks
   bDefine following terms- Net pressure, Ultimate bearing capacity, Net ultimate bearing capacity, Net safe bearing capacity and Allowable bearing pressure.
   How to answer

   • Define net pressure = gross minus overburden
   • Define ultimate, net ultimate, net safe with FOS
   • Define allowable bearing pressure with settlement consideration
3. 7 Marks
   aExplain the concept of general shear failure.
   How to answer

   • Define general shear failure with Terzaghi mechanism
   • Describe failure surfaces and load-settlement curve
   • Contrast with local and punching shear failure
4. 7 Marks
   bA 12 m long, 300 mm dia concrete pile is driven in a uniform deposit of dense sand. Water table is at great depth and is not likely to rise. The avg dry unit wt. of sand is $18\text{ kN/m}^3$. Use $N_q = 137$, calculate the safe load capacity of a single pile with a FOS of 2.5, $\alpha = 25^\circ$.
   How to answer

   • Compute effective overburden at pile tip
   • Compute end bearing using $Q_p = A_p \sigma'_v N_q$
   • Compute skin friction and safe load with FOS 2.5
5. 7 Marks
   aFor 450 mm side square section concrete pile 15 m long is driven in a deep deposit of uniform clay. The laboratory unconfined compression test on undisturbed sample indicates an avg value of UCS $(Q_u) = 75\text{ kN/m}^2$. Calculate the ultimate load capacity of pile. Take $\alpha = 0.8$, $\gamma_{sat} = 18\text{ kN/m}^3$, $\gamma_w = 10\text{ kN/m}^3$.
   How to answer

   • Determine undrained cohesion $c_u = Q_u/2$
   • Compute skin friction $Q_s = \alpha c_u A_s$
   • Compute end bearing $Q_p = 9 c_u A_p$ and $Q_u = Q_p+Q_s$
6. 7 Marks
   bGive the classification of pile based on function or action.
   How to answer

   • Classify by function: end bearing, friction, etc.
   • Classify by action/installation effect
   • Give examples for each type
7. 7 Marks
   aList the various equipments used for field compaction. Also differentiate between light weight and heavy weight proctor test.
   How to answer

   • List rollers, rammers, vibratory equipment
   • Define light vs heavy Proctor: hammer weight, drop, layers
   • Compare energy and uses
8. 7 Marks
   bDescribe the SPT method in brief. Also explain over burden and dilatancy correction on N value.
   How to answer

   • Describe SPT procedure, sampler, blow count N
   • Explain overburden correction formula
   • Explain dilatancy correction for saturated fine sand
9. 7 Marks
   aWhy and in which situations soil stabilization techniques are required in field? Describe the electrical stabilization technique for improvement of soil.
   How to answer

   • Explain need: weak, expansive, permeable soils
   • List situations requiring stabilization
   • Describe electrical stabilization: electro-osmosis, electrodes
10. 7 Marks
    bDescribe the Geosynthetics used for soil improvement technique.
    How to answer

    • Define geosynthetics types: geotextile, geogrid, etc.
    • Explain functions: separation, reinforcement, drainage
    • Give field applications
11. 7 Marks
    aExplain various characteristics of expansive and collapsible soils.
    How to answer

    • Define expansive soils: swelling, montmorillonite
    • Define collapsible soils: sudden settlement on wetting
    • List index and engineering characteristics
12. 7 Marks
    bExplain:

    1. i)Disturbed and undisturbed sample
    2. ii)CNS layer
    How to answer

    • Distinguish disturbed vs undisturbed samples and uses
    • Define CNS layer purpose for expansive soils
    • Explain placement and thickness concept
13. 7 Marks
    aWhat are various types of lateral earth pressure? Derive the expression for calculating earth pressure at rest.
    How to answer

    • List at-rest, active, passive pressures
    • Derive $K_0$ expression with lateral strain condition
    • State $K_0 = \mu/(1-\mu)$ and Jaky relation
14. 7 Marks
    bFor an earth retaining structure shown in fig.1, construct earth pressure diagram for active state. Also find the total thrust per unit length of wall.

    How to answer

    • Compute $K_a$ for $\phi=30^\circ$ and unit weights from $G,e$
    • Draw active pressure distribution with surcharge and water
    • Integrate to get total thrust per unit length
15. 14 Marks
    A retaining wall of 5 m height has to retain a stratified backfill as shown in fig.2. Find out the magnitude of total active thrust on the wall and locate the point of application.

    How to answer

    • Compute $K_a$ for each layer with $c-\phi$ and granular soils
    • Compute active pressures at B, C, D interfaces
    • Sum thrusts and take moments for line of action