Soil Mechanics, Materials, & Testing Flashcards
What is a quick clay?
What is a dispersive soil?
Highly erodible clays that often appear as “normal clear”
Difficult to identify from visual inspection/common index tests
What is a collapsible soil?
Fine sand and silt with loose structure and weak inter-particle bonds.
Potential for collapse and highly erodible
What soil types does immediate (also known as elastic) settlement occur in?
All Types
When does immediate/elastic settlement occur?
During and right after construction
What is the dominant settlement in cohesionless, granular, coarse-grained soils?
Immediate/Elastic
What is another term for immediate settlement?
Elastic settlement
What is the dominant settlement in clay?
Primary consolidation
Why does primary consolidation occur in clays?
Due to the slow drainage of porewater with excess pressure due to loading
What causes secondary settlement
Particle rearrangement and creep
Primary consolidation takes a ____ time and is _____
long, substantial
Normally Consolidated (NC) Clay
The current effective overburden pressure is equal to the max pressure the soil has been subjected to in the recent past.
Overconsolidated (OC) Clay
The current effective overburden pressure is less than the max pressure the soil has been subjected to in the recent past.
Water has a _____ effect on the internal friction angle of cohesionless (gravels, sands) soils. However, the effective stress ______ which causes a _______ overall shear resistance.
negligible, decreases, lower
An increased water content of clay results in ______ shear strength and _____ cohesion.
decreased, decreases
How do you determine D60, D10, etc.
It is the average grain size for the amount passing the X%. Need the chart.
Liquid Limit
Moisture content at which the soil goes from a plastic state to a liquid state.
Plastic Limit
Moisture content at which the soil goes from a semisolid to a plastic state.
A higher PI indicates a higher ________ and _________.
clay particle content and chance of problems (swell potential and heave)
Liquidity Index (LI)
Relates the moisture content of soil to PI
Tensile Stress
When a material stretches or increases in length from the addition of a force.
Compressive Stress
When a material shortens or decreases in length from the addition of a force.
Shear Stress
Force at which sections or layers move in opposite directions.
Define a Poorly Graded Soil
Uneven distribution of soil sizes
