Soils Flashcards
(19 cards)
What are the two main types of soil and the sub categories
Granular and cohesive
Soft granular
Hard granular
Clay minerals
Plant residue
What are the two types of soil particle analysis and when are each used
Sieve analysis - >0.063
Laser analysis- <0.063
What is the definition of a granular soil
A soil that is formed of sand and gravels
What is the definition of a cohesive soil
A soil is a soil that is made up of particles bound together by clay minerals. The particles are usually flaky and sheet like and retain some water on their surfaces
What is the definition of cohesion in soils
Cohesion is the shear strength that is interdependent of the particles friction
What is the definition of true and apparent cohesion
True cohesion is when electrostatic forces keeps clays stiff
Apparent cohesion is cohesion caused by negative water pore pressure
What are clays made up of
Clay minerals are made up of hydrates of aluminium ,
iron
and magnesium silicate
What are Atterberg limits and what are the two limits
Atterberg limits are limits under which the behavior of soil changes,
Plastic and liquid Atterberg limits
What is the plastic Atterberg limit
The moisture content at which the material deforms without cracking
What is the liquid Atterberg limit
The moisture content at which the material flows under its own weight
also the plasticity index is liquid-plastic limits
What is effective stress and what is the equation for it
Effective stress is the stress experienced once water saturated is taken into account
Effective stress = total tress - pore water pressure
What is the shrinkage Atterberg limit
The moisture content at which further loss of moisture does not cause volume loss
What is the equation for water pressure
Water pressure = depth below water table x density x gravity
What is consolidation in clays
Consolidation is when water is ‘squeezed’ out under a heavy load
causing moisture levels and volume to decrease
and an increase in strength in the long term
What are some of the main differences between drained and undrained soil behavior
In drained, water can be squeezed out whereas in undrained it cannot
In undrained, as total pressure increases so does pore water pressure
In drained, effective and shear stress increases with time but in undrained it does not
How does soil react with different types of stress
Compressive-effective
Shear-large variation, dependent on friction and cohesion
Tension- very ineffective
What is friction angle
The angle of a mound of the material
at which it will slip under its own weight
