Abstract: Based on strain control consolidated undrained triaxial tests, stress-strain relationship and strength characteristic of expansive mud-stone are investigated and analyzed. The results show that the stress-strain relationship appears strain softening, and joints in mud-stone are important factor that influences strength characteristic. Different failure modes have different stress-strain relationships. Furthermore, the results also show that the peak strength, residual strength and residual strength ratio change with variation of confining stress, and development of pore pressure has three stages. By controlling shear speed ratio of triaxial test, influences of shear speed ratio on the stress-strain relationships and strength characteristic are discussed.

Key words: expansive mud-stone, strain softening, strength, shear speed ratio