BCE Geotechnical 4

Question 1

A pile foundation transfers load primarily through skin friction along its length. What type of pile is this classified as?

Accepted Answer

Friction pile

Answer

Friction (or floating) piles rely on skin friction along the pile shaft rather than point resistance at the tip to carry axial loads.

Question 2

What is the primary advantage of the Mohr-Coulomb failure criterion expressed as τf = c' + σ'n tan φ'?

Accepted Answer

It provides a linear relationship between shear strength and effective normal stress

Answer

The Mohr-Coulomb criterion linearly relates peak shear strength to effective normal stress through cohesion intercept c' and friction angle φ', making it practical for design.

Question 3

What is the purpose of a filter layer placed behind a retaining wall or around a drainage pipe?

Accepted Answer

Prevent fine soil particles from migrating into the drainage system while allowing water to flow freely

Answer

Filters must satisfy geometric criteria (D15,filter/D85,soil < 5) to retain fines while remaining permeable enough to relieve pore pressure.

Question 4

A normally consolidated clay has c' = 0. If the friction angle φ' = 28°, what is the active earth pressure coefficient Ka?

Accepted Answer

0.361

Answer

Ka = tan²(45 − φ'/2) = tan²(45 − 14) = tan²(31°) ≈ 0.361.

Question 5

What geotechnical phenomenon occurs when loose saturated sand loses strength suddenly due to cyclic loading and behaves like a liquid?

Accepted Answer

Liquefaction

Answer

Liquefaction occurs when cyclic earthquake loading causes excess pore pressure to build up equal to total confining stress, eliminating effective stress and shear strength in loose saturated sand.

BCE - Bachelor of Civil Engineering Practice Test

BCE - Bachelor of Civil Engineering Practice Test

BCE Geotechnical 4