Civil Engineering PE Geotechnical Engineering and Slope Stability 2

Question 1

A cantilever retaining wall achieves overturning resistance primarily from:

Accepted Answer

Weight of retained soil over the heel of the base slab

Answer

The heel of the base slab extends under the retained fill so that soil weight over the heel contributes to the overturning resistance.

Question 2

The minimum acceptable factor of safety against sliding for a retaining wall is typically:

Accepted Answer

1.5

Answer

AASHTO and most codes require FS ≥ 1.5 against sliding, computed as total horizontal resisting forces divided by total active horizontal thrust.

Question 3

The modified Proctor compaction test (ASTM D1557) delivers approximately how many times more compactive energy than the standard Proctor (ASTM D698)?

Accepted Answer

4.5×

Answer

The modified Proctor uses a 10-lb hammer with an 18-in drop in 5 layers, delivering roughly 4.5 times the energy of the standard Proctor.

Question 4

Primary consolidation settlement for a normally consolidated clay is calculated using:

Accepted Answer

S = Cc/(1+e₀) × H × log(σ′f/σ′i)

Answer

For NC clay, S = [Cc/(1+e₀)] × H × log(σ′f/σ′i), where Cc is the compression index and e₀ is the initial void ratio.

Question 5

The dimensionless time factor Tv in Terzaghi's consolidation theory is defined as:

Accepted Answer

Tv = cv × t / Hdr²

Answer

Tv = cv·t/Hdr², where cv is the coefficient of consolidation and Hdr is the length of the drainage path.

Civil Engineering PE Practice Test