TABLE OF CONTENTS At the beginning of this chapter on the shear strength of cohesive soil (Sec. 9.1), it was stated that the shear strength could be divided into three broad groups:
Undrained shear strength. This includes undrained shear strength measured directly from field or laboratory tests s u, or the undrained shear strength in terms of the total stress parameters, c and ? (Secs. 9.3 and 9.4).
Drained shear strength. The drained shear strength can be obtained from drained shear strength tests, although a more common approach is to perform consolidated undrained triaxial compression tests with pore water pressure measurements which are used to obtain the shear strength in terms of the effective stress parameters, c ? and ? ? (Sec. 9.5).
Drained residual shear strength. The drained residual shear strength has been discussed in Sec. 9.1. The residual shear strength ? ? r is defined as the remaining (or residual) shear strength of cohesive soil after a considerable amount of shear deformation has occurred. In essence, ? ? r represents the minimum shear resistance of a cohesive soil along a fully developed failure surface. The drained residual shear strength is primarily used to evaluate slope stability, where there is a preexisting shear surface. Examples include ancient landslides, slopes in overconsolidated fissured clays, and slopes in fissured shales. The drained residual shear strength may also be applicable for other types of preexisting shear surfaces, such...
