Foundation & Soil Analysis Flashcards
7 cards from real CCI practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Foundation & Soil Analysis flashcards as text
Which failure mode is represented by a 'Rankine failure wedge' in a retaining wall analysis?
Answer: Active earth pressure causing sliding or rotation of the wall
Rankine's active earth pressure theory defines a triangular failure wedge behind the wall that creates lateral thrust on the structure.
A construction inspector notices that fill compaction test results consistently fall below 95% of maximum dry density. The most likely corrective action is:
Answer: Adjust moisture content toward optimum and re-compact in thinner lifts
Failing compaction tests most often indicate moisture content is too wet or dry; adjusting to optimum and reducing lift thickness typically corrects the problem.
In the context of earth pressure, 'at-rest' pressure (K0) condition occurs when:
Answer: The retaining structure does not move laterally
K0 (coefficient of earth pressure at rest) applies when the wall undergoes no lateral movement, keeping soil in its natural stress state.
Which condition must be met for a soil to be considered 'expansive' or 'swelling' soil?
Answer: High plasticity index and high percentage of montmorillonite clay minerals
Expansive soils typically have high PI (>35) and contain montmorillonite (smectite) minerals that absorb water and expand significantly.
A soil boring encounters 'refusal' during SPT testing. This most likely means:
Answer: Very dense or hard material that prevents further penetration
SPT refusal is defined as 50 blows for less than 6 inches of penetration, indicating very dense granular soil, hard rock, or obstructions.
What is the primary function of a geosynthetic separator fabric placed between subgrade soil and aggregate base course?
Answer: Prevent migration of fines from subgrade into the aggregate layer
Separator geotextiles prevent intermixing of fine-grained subgrade soils with the aggregate base, maintaining drainage and structural integrity.
During inspection of a spread footing excavation, the inspector finds the bearing stratum is softer than anticipated. The best immediate course of action is:
Answer: Notify the engineer of record and suspend concrete placement pending evaluation
Unexpected soil conditions must be reported to the engineer of record before proceeding so the design can be re-evaluated if necessary.