Strength Variation Along Failure Surfaces in Clay

Experimental studies have shown that the undrained strength of one-dimensionally consolidated clay may vary with orientation of the failure plane. Three of the types of variation found by trimming unconsolidated-undrained compression test specimens in different directions are shown in Fig. 1. Variations of undrained strength such as those shown in Fig. 1 may result from anisotropy with respect to the values of the effective stress strength parameters, or anisotropy with respect to development of changes in pore-water pressures, or both; they may also result from reorientation of the principal stress directions during sampling and testing.