Postcyclic undrained strength for Cohesive Soils

The undrained strength of saturated cohesive soils after cyclic loading decreases and increases depending on whether the soil is initially normally consolidated or overconsolidated and whether drainage is included during or after cyclic loading. The methods for predicting these changes due to both strength degradation and its recovery in saturated cohesive soils after cyclic loading are presented in the current paper. The experimental parameters included in the proposed equations are easily determined as a function of plasticity index. The applicability of the methods is shown by investigating the results from both cyclic triaxial and direct simple shear tests on various kinds of normally consolidated cohesive soils including highly sensitive clays and peat. It is suggested from this consideration that they are valid for the prediction of the undrained strength for cohesive soils after cyclic loading with and without drainage.