## What is undrained shear strength?

The undrained shear strength (su) is defined as the peak value of the horizontal shear stress. Direct-Simple Shear Test. The direct-simple shear test is conducted on a cy- lindrical sample encased in a wire-reinforced rubber membrane.

Why does the undrained strength of a normally consolidated clay increase with depth?

It generally varies over depth as a function of insitu confining stress at a given depth. Note that larger confining stress reduces void ratio over the historical time. By the decrease of void ratio, undrained shear strength increases.

### What is remoulded undrained shear strength?

The remolded shear strength is considered the undrained shear strength following significant shearing wherein the fabric has been largely destroyed without a change in water content (Mitchell and Soga 2005; ASTM D 2573).

What is the undrained shear strength of sand?

Typical values of shear strength

Undrained shear strength su (kPa)
Compact sands 0 35° – 45°
Loose sands 0 30° – 35°
Unweathered overconsolidated clay
critical state 0 18° ~ 25°

#### Can be used to determine in place shear strength for soft clay soils?

Vane shear test: It is used to determine the undrained shear strength of soils, especially soft clays. This test can be done in a laboratory or in the field directly on the ground.

What is consolidated undrained soil?

A triaxial consolidated undrained compression test is carried out to determine the shear strength of the soil. The pores pressure of the soil is measured and the soil is consolidated under pressure from all around in a triaxial cell before failure is induced by increasing the major principal stress.

## Is the shear strength of the soil the same under drained and undrained conditions?

In reality, soil is partially drained, somewhere between the perfectly undrained and drained idealized conditions. The shear strength of soil depends on the effective stress, the drainage conditions, the density of the particles, the rate of strain, and the direction of the strain.

What is drained and undrained condition of soil?

Drained soil is that from which the free moisture has withdrawn. Undrained soil is the one in which the free moisture in the soil has not withdrawn from it. The strength of the soil depends to an extent on its drained / undrained condition.

### Why is undrained shear strength important?

The undrained cyclic shear strength has to be evaluated to calculate the capacity under cyclic loads. The undrained cyclic shear strength should be obtained for various stress paths. The remolded shear strength is an important parameter because it is used to calculate the penetration resistance of the skirt walls.