## What is CU of clay?

The undrained shear strength (cu) is considered one of the most basic para- meter characterizing soils in engineering practice. The particular importance of cu is in the case of clayey soil. All analysed clay specimens were taken from the large depth, up to 303 m below terrain level.

## How do you get undrained shear strength?

- is the shear strength (σ1 – σ3)/2.
- hence, = Su (or sometimes cu), the undrained strength.
- = σ’ tan(φ’) + c’
- φ’ = the effective stress friction angle, or the ‘angle of internal friction’ after Coulomb friction. The coefficient of friction.
- Use in practice: If one is to adopt critical state theory and take c’ = 0; p

**What is C in geotechnics?**

c’ is the ‘cohesion’ intercept. In soils, the Mohr-Coulomb criterion applies when the normal stress is an effective normal stress.

### How do you find the undrained strength of soil?

The principal stress difference (deviator stress) (P1 – P3) is computed as the axial piston load divided by the corrected area of the sample and plotted as a function of the axial strain. The undrained shear strength (su) is defined as one-half of the peak value of (P1 – P3).

### What is the difference between drained and undrained shear strength?

Drained Shear Strength: The soil is free to dilate or contract during shear if the soil sample is totally drained. Undrained Shear Strength: Whenever water is not allowed to flow in or flow out of the soil then the stress path is called as undrained stress path.

**What is the undrained strength?**

The undrained shear strength (su) is defined as one-half of the peak value of (P1 – P3). For CU tests, the slower strain rates of Raymond should be retained to more closely approximate field rates of loading. The UU test provides a measure of Su at the in situ water content of the sample.

#### Is undrained cohesion and undrained shear strength the same?

Based on analysis that undrained shear strength coincides with 50 percentile of distribution data meanwhile undrained compressive strength is around twice of cohesion for testing using unconfined pressure. This relationship is the most familiar equation.

#### Is cohesion the same as undrained shear strength?

**Is undrained shear strength the same as undrained cohesion?**

undrained shear strength (Sul is assumed equal to the cohesion intercept (cul of the Mohr-Coulomb envelope for total stresses. For these assumptions the undrained strength of a saturated clay is not affected by changes in confining stress so long as the water content does not change.

## What is the difference between drained and undrained 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.