BCE Geotechnical 5

Question 1

What is the primary purpose of a geosynthetic reinforcement layer placed within a compacted fill embankment?

Accepted Answer

Provide tensile resistance to improve embankment stability and reduce lateral spreading

Answer

Geogrid or geotextile reinforcement carries tensile stress that soil cannot, improving overall embankment stability and controlling lateral deformation at the base.

Question 2

Which slope stability method satisfies both force and moment equilibrium for each slice and is considered the most rigorous?

Accepted Answer

Spencer's Method

Answer

Spencer's method assumes a constant interslice force inclination and satisfies both overall moment and force equilibrium, making it one of the most complete methods.

Question 3

A soil profile shows SPT N-values of 2-4 in the upper 5 m followed by N > 50 below. What foundation type is most appropriate for a heavily loaded column?

Accepted Answer

Deep pile foundation driven to the dense layer

Answer

N = 2–4 indicates very soft to soft ground incapable of supporting heavy loads; deep piles driven to the dense bearing stratum (N > 50) are required.

Question 4

What is the definition of the overconsolidation ratio (OCR)?

Accepted Answer

Ratio of preconsolidation pressure to current vertical effective stress

Answer

OCR = σ'p / σ'v0; OCR = 1 means normally consolidated, OCR > 1 means overconsolidated, indicating the soil has experienced higher stresses in its past.

Question 5

During a triaxial CD test on dense sand, what typically occurs to pore pressure and volume as shear strain increases past peak?

Accepted Answer

Negative pore pressure develops and volume increases (dilative)

Answer

Dense sand dilates (expands) during shear in a drained test; in undrained conditions this would manifest as negative (suction) pore pressures.

BCE - Bachelor of Civil Engineering Practice Test

BCE - Bachelor of Civil Engineering Practice Test

BCE Geotechnical 5