Soils and Geology Flashcards
7 cards from real CLARB practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Soils and Geology flashcards as text
Which ASTM standard governs the Standard Proctor compaction test used to determine optimal moisture content for maximum dry density?
Answer: ASTM D698
ASTM D698 defines the Standard Proctor test using standard compaction energy; ASTM D1557 is the Modified Proctor test with higher compaction energy.
Which soil condition presents the greatest risk for building foundations and hardscape due to volumetric changes with moisture fluctuations?
Answer: Expansive clay soils
Expansive clays (high in montmorillonite) swell significantly when wet and shrink when dry, causing differential movement that damages foundations and pavements.
The angle of repose is a critical soil engineering property that most directly influences which landscape design consideration?
Answer: Slope stability and cut/fill grading design
The angle of repose defines the steepest angle at which loose soil remains stable; it directly dictates maximum allowable slope gradients for cut and fill sections.
What does soil bearing capacity describe in the context of landscape construction?
Answer: The maximum load per unit area soil can support without failure or excessive settlement
Bearing capacity defines the maximum stress the soil can withstand before shearing or settling excessively, which is critical when designing structures, walls, and pavements.
Liquefaction — where saturated soil temporarily loses strength and behaves like a liquid — is most commonly triggered by which event?
Answer: Seismic (earthquake) activity
Earthquakes generate rapid cyclic loading that increases pore water pressure in saturated, loose granular soils until effective stress drops to zero, causing liquefaction.
What is the primary purpose of conducting a soil percolation test on a landscape site?
Answer: Measuring the rate at which soil absorbs water for drainage or infiltration system design
Percolation tests measure how quickly water drains through soil, which is essential for sizing septic drain fields, rain gardens, bioretention cells, and other infiltration-based stormwater features.
Which phenomenon occurs when soil consolidates vertically under the weight of overlying fill or structures over time?
Answer: Settlement/consolidation
Consolidation is the time-dependent compression of fine-grained saturated soils as pore water is slowly squeezed out under sustained load, causing gradual vertical settlement.