Abstract: The triaxial compression experiments under different confining pressures for sandy slate samples have been conducted by MTS815 Flex Test GT rock mechanics test system. The anhydrous post-peak strength of the cracked rock mass is tested during the experiment. Then the residual strength of the cracked rock mass under different pore pressures is obtained by applying 4-levels dynamic and static pore pressures on the crack surface of the samples. The experiment results show that the mechanism of the influence on the strength of cracked rock mass caused by water mainly includes following aspects: saturated softening and pore pressure weakening. The saturated softening affection does not change with the changes of pore pressure; and the pore pressure weakening affection increases with the increasing of pore pressure linearly; which mainly influences the cohesive force while almost no effect on the internal friction coefficient. The weakening affection of static pore pressure is stronger than dynamic pore pressure’s. Through testing and analysis, the quantitative expression of the comprehensive effect of saturated softening affection and pore pressure weaken affection on cracked rock mass is obtained; and the engineering application of such results is discussed.

Key words: sandy slate, cracked rock mass, post-peak strength, saturated softening, pore pressure weakening