Foundation & Soil Analysis Flashcards

A cone penetration test (CPT) measures which of the following directly?

Answer: Tip resistance and sleeve friction

CPT directly measures cone tip resistance (qc) and sleeve friction (fs), from which soil type and strength are interpreted.

Which retaining wall type relies on the weight of the wall itself and retained soil above its base to resist overturning?

Answer: Gravity retaining wall

Gravity retaining walls use their own mass (concrete, stone, or masonry) to resist lateral earth pressure without requiring reinforcement.

When inspecting a drilled shaft (caisson), the inspector's primary concern at the bottom of the shaft prior to concrete placement is:

Answer: Removal of loose or disturbed material from the bearing surface

Loose cuttings or disturbed soil at the shaft bottom must be removed or cleaned out to ensure proper end bearing.

The coefficient of permeability (k) in Darcy's Law represents:

Answer: The ease with which water flows through a soil

Darcy's Law states flow velocity = k × hydraulic gradient; k (permeability) reflects how easily water moves through soil pores.

A soil with a relative density (Dr) of 85% is best classified as:

Answer: Dense

Relative density above 75% is classified as dense; Dr = (emax − e)/(emax − emin) × 100%.

What does the term 'frozen pile' refer to in pile driving operations?

Answer: A pile that cannot be advanced further due to soil set-up after interruption

Soil set-up (freeze) occurs when a pile becomes harder to drive after a driving pause because pore pressures dissipate and soil strength regains around the pile.

Which soil improvement technique uses vertical drains and preloading to accelerate consolidation settlement before construction?

Answer: Prefabricated vertical drains (wick drains) with surcharge fill

Wick drains shorten drainage paths to accelerate pore pressure dissipation; combined with a surcharge, this speeds up primary consolidation.