Abstract: Based on the consolidated undrained triaxial tests, the strain softening behaviour and the residual strength characteristic of normally or overconsolidated diatomaceous mudstones were invesitigated. The relationship between residual strength ratio and consolidation pressure were studied. The stress-strain curves and the residual strength of intact specimens(no joint) and precut specimens having a single joint are compared.The effect of a single joint with different inclinations on the residual strength properties were discussed.