If of

If the sides of the cylindrical specimen are not acted on by the horizontal pressure 0"3' the load required to cause failure is called the unconfined compressive strength qu. It is obvious that an unconfined compression test can be performed only on a cohesive soil. According to Eq. (8:20), the unconfined compressive strength qu is equal to

or the shear strength

(8.23) (8.24a)

(8.24b)

Eq. (8.24b) shows one of the simplest ways of determining the shear strength of cohesive soils.