Undrained Shear Strength Characteristics of Natural Silty Clay

Triaxial consolidation undrained shear tests were carried out on both undisturbed and reconstituted samples of natural silty clay to investigate their undrained shear strength characteristics. Test results suggest that the strength envelope of the undisturbed sample is composed by two straight lines, which is different from that of the strength envelopes of reconstituted samples showing a straight line through the origin. Undrained shear strength of undisturbed samples are larger than corresponding reconstituted samples due to the resistance of soil structure in the pre-yield stress state. In the post-yield stress state, however, strength envelope of the undisturbed sample lies among the reconstituted samples with different initial water contents. Undrained shear strength for undisturbed samples in the post-yield stress state and reconstituted samples can be well correlated with the water content under different confining stress, which implies that undrained shear strength mainly depends on the current water content.