Abstract: The mechanical properties of shale vary after being soaked and softened in water. In view of this, triaxial compression tests were conducted on shale soaked in water for different durations. The relationship between stress and strain of soaked shale was revealed, and the variation regularity of mechanics parameters of shale was obtained under the action of water deterioration. Results indicate that the strength and elastic modulus of soaked shale specimens reduced greatly with the increase of soaking duration. Water soaking had small influence on frictional angle of soaked shale, but significant impact on cohesion. In addition, as the softening effect became increasingly significant, the failure mode of shale specimens gradually changed from brittle tensile splitting failure to a mixed failure form of tension and shear. The strength reduced and ductility increased when softening action became increasingly significant. Soaking duration has significant impact on strength, deformation and failure mode. The results offer reference for determining geotechnical parameters or mechanical analysis of shale.

Key words: shale, softening action, soaking time, triaxial compression test, mechanical characteristics, stress-strain curve