Geotechnical Engineering and Slope Stability Flashcards
6 cards from real Civil Engineering PE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Geotechnical Engineering and Slope Stability flashcards as text
A cantilever retaining wall achieves overturning resistance primarily from:
Answer: Weight of retained soil over the heel of the base slab
The heel of the base slab extends under the retained fill so that soil weight over the heel contributes to the overturning resistance.
The minimum acceptable factor of safety against sliding for a retaining wall is typically:
Answer: 1.5
AASHTO and most codes require FS ≥ 1.5 against sliding, computed as total horizontal resisting forces divided by total active horizontal thrust.
The modified Proctor compaction test (ASTM D1557) delivers approximately how many times more compactive energy than the standard Proctor (ASTM D698)?
Answer: 4.5×
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.
Primary consolidation settlement for a normally consolidated clay is calculated using:
Answer: S = Cc/(1+e₀) × H × log(σ′f/σ′i)
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.
The dimensionless time factor Tv in Terzaghi's consolidation theory is defined as:
Answer: Tv = cv × t / Hdr²
Tv = cv·t/Hdr², where cv is the coefficient of consolidation and Hdr is the length of the drainage path.
Soil liquefaction during an earthquake is most likely to occur in:
Answer: Loose, saturated, fine sand
Liquefaction occurs when cyclic shear stresses generate excess pore pressure equal to effective confining stress, most easily triggered in loose saturated sands.