Key Concepts Flashcards
(13 cards)
What are the causes of weathering
Water, wind, temperature change, gravity, chemical interaction, living organisms, pressure deffrences
When do landslides occur
When the shear stress due to gravity is greater than the shear resistance of the soils
What is the design life of structures and what are the extreme design scenarios
120years - structures are designed for two extreme scenarios, short-term and long-term
What are the short-term and long-term conditions
Short-term - undrained, water within soil
Long-term - drained, no water within soil, therefor water pressure is zero.
What is the method to test plastic limit
Rolling thread method
What is the method to test liquid limit
Cone penetrometer
What is the plasticity index PI
The water content range in the plastic solid phase. PI=WL-WP
What is water absorption like when surface area is changed
The higher the surface area, the greater the water absorption, therefore the smaller the particle the greater the water absorption
What is saturation like above and below the water table
Above- unsaturated (0%-100%)
Below- saturated 100%
Unit weight
Weight per unit volume (N/m^3)
What does “effective”/“ ‘ “ mean
Long-term, drained, therefore e.g unit weight saturated minus unit weight water. Effective unit weight ≈ dry unit weight
Effective stress principle
It is the effective stress (rather than total stress) which determines the shear strength and volume change behaviour of soils
Relationship between water pressure and shear resistance between particles
The increase in water pressure between 2 particles reduces the force between them, therefore reduced the shear resistance between them, causing the particles to slide between each other more easily
