CE 618 Quiz 4 2024

Boltzmann transformation provides the solution to the theta form of Richard’s equation for

transient flow through soils.

Green-Ampt method provides a solution to Richards' transient flow equation

Solution to Richrds' equation yields unsaturated steady-state flow behaviour

Unsaturated sandy soils show cohesion intercept on the σ − τ plot obtained from suction

controlled triaxial tests.

In Bishop’s effective stress equation, c’ and ϕ′ are material constant and c is a state variable.

Water retention tests and suction controlled direct shear tests are conducted on unsaturated silty

soil. The relationship between effective stress parameter χ and degree of saturation can be

established using Bishop’s modified M-C criterion.

The extended M-C criterion (Fredlund et al., 1978) for shear strength of unsaturated soil represents

a curved surface in t, σ -ua and ua-uw space.

The Bishop’s effective stress equation can also be written as σ′= σ − u ( a) + X (σ − u ( w))

based on the null-type tests.

The slope on the curve τf vs (ua-uw)f

over a wide suction range for clayey soil is constant, under a given net normal stress (σ − ua)

and having value of tan ϕ ( b)

As c f decreases, the strength parameter ϕb consistently increases with suction.