Foundation & Soil Analysis Flashcards

Which condition describes 'quick condition' or 'quicksand' in cohesionless soils?

Answer: Upward seepage force equals the effective weight of the soil

Quick condition occurs when upward hydraulic gradient causes seepage force to equal the buoyant weight of soil, eliminating effective stress.

A geotechnical inspector observes 'heave' at the bottom of an excavation in soft clay. The most likely cause is:

Answer: Insufficient passive resistance against base instability

Bottom heave in soft clay excavations results from inadequate shear strength to resist the net vertical stress difference at the base.

In a soil boring log, the abbreviation 'SP' under USCS refers to:

Answer: Poorly graded sand

SP = Poorly Graded Sand in the Unified Soil Classification System, indicating uniform or gap-graded sand with insufficient fines.

Which laboratory test determines the maximum dry density and optimum moisture content of a soil?

Answer: Proctor compaction test

The Proctor compaction test (standard or modified) establishes the compaction curve to find maximum dry density at optimum moisture content.

What is the primary purpose of a surcharge load applied near an existing foundation?

Answer: It increases lateral earth pressure on the foundation or retaining structure

A surcharge near a foundation or retaining wall increases the lateral earth pressure that must be resisted by the structure.

For a driven steel H-pile, 'plugging' refers to:

Answer: Soil trapped inside the flanges acting as part of the pile toe

Plugging occurs when soil becomes trapped between the flanges of an H-pile, effectively increasing the end-bearing area.

Which of the following best describes 'differential settlement'?

Answer: Unequal settlement between two points on a structure causing distortion

Differential settlement is the difference in settlement between two points, which can cause structural distortion, cracking, or tilting.