Elastic Soils Flashcards
What is the difference between true and engineering (or nominal) strains?
True strains consider the current specific volume, whereas engineering strains consider the initial specific volume at the start of straining
How do you convert engineering strains to true strains?
εt = -ln(1-εn)
What must you remember about volumetric strain calculations?
Volumetric strain is always 0 in undrained loading
What is the condition for the elastic model in soils?
Strain is less than ~0.5%
Under what conditions are δp’ and δεd independent?
The soil is isotropic and elastic
What should be true of the stiffness matrix for an elastic soil?
It is diagonally symmetrical
How can εv be calculated using Δp’?
εv = Δp’/K’
How do you find the anisotropic axial strain increment from the stress increments?
δεa = 1/E’v(δσ’a) - 2ν’vh/E’v(δσ’r)
How do you find the anisotropic radial strain increment from the stress increments?
δεr = (1-v’hh)/E’h(δσ’r) - v’vh/E’v(δσ’a)
What is anisotropy?
When a material has different properties in different directions
What class of constitutive models can represent anisotropic plastic behaviour in soils? Why can they achieve this?
S-CLAY1 models
They incorporate the anisotropic evolution of the yield surface as it grows larger and become inclined
How are drained and undrained Young’s modulus related?
Eu = 3E’/2(1+v’)
What are the values of Ku, Gu and vu?
Ku = infinity
Gu = G’
vu = 0.5
