Practice Test GeeksBCE - Bachelor of Civil Engineering Practice Test
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Geotechnical Flashcards

7 cards from real BCE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Geotechnical flashcards as text

  1. A retaining wall has a saturated backfill with a water table at the surface. How does the presence of water affect the total lateral pressure on the wall?

    Answer: Increases total pressure significantly due to hydrostatic water pressure added to earth pressure

    With a high water table, both the effective earth pressure (using submerged unit weight) and full hydrostatic water pressure act on the wall, greatly increasing total lateral force.

  2. What is the significance of the preconsolidation pressure (σ'p) in soil mechanics?

    Answer: Maximum past effective stress the soil has experienced

    σ'p is the maximum effective stress the soil has ever been subjected to; stresses below it cause small elastic (recompression) settlements, while stresses above cause larger virgin consolidation settlements.

  3. Which method is most appropriate to determine the in-situ undrained shear strength of a soft sensitive clay?

    Answer: Field Vane Shear Test (VST)

    The field vane shear test directly measures peak and remolded undrained shear strength of soft clays without disturbing the sample.

  4. What is critical hydraulic gradient (ic) in the context of piping failure?

    Answer: Upward hydraulic gradient at which seepage forces reduce effective stress to zero

    ic = (Gs − 1)/(1 + e) ≈ 1 for most soils; when the upward seepage gradient reaches ic, effective stress becomes zero and the soil loses stability (quick condition or piping).

  5. In a direct shear test, peak shear stress occurs before residual shear stress. What does the residual shear strength represent?

    Answer: Long-term strength after large displacement when soil structure is fully remolded

    Residual strength corresponds to the minimum, post-peak strength after clay platelets have aligned parallel to the shear surface following large displacement.

  6. What does the term 'sensitivity' (St) of clay describe?

    Answer: Ratio of peak undrained shear strength to remolded undrained shear strength

    St = su(peak)/su(remolded); high sensitivity (>8) indicates quick clays that lose most strength upon disturbance.

  7. Which compaction curve characteristic is most directly affected by increasing compaction energy in a Standard Proctor test?

    Answer: Optimum moisture content decreases and maximum dry density increases

    Higher compaction energy shifts the curve upward and to the left: maximum dry density increases and optimum moisture content decreases.