Shear Strength of Soils and Cyclic Loading

This paper describes the results of undrained triaxial tests on undisturbed samples of three soils: (1)A slightly clayey silt; (2)a silty clay; and (3)a sand. The static undrained loading tests to failure were performed after various numbers of cycles of undrained cyclic loading as well as with no previous cyclic loading. No drainage was allowed between undrained cyclic loading and the undrained monotonic shearing. The ultimate undrained shear strength was essentially independent of the previous cyclic loading, but it did correlate well with the void ratio. The modulus of deformation was greatly reduced by the cyclic loading. Therefore, the major effect of undrained cyclic loading on the subsequent undrained behavior is to increase the strains while the available ultimate strength is largely unchanged.