An experimental and theoretical investigation of time-dependent cracking and creep behavior of rocks under triaxial hydro-mechanical coupling

Abstract

Subcritical crack propagation and rock creep deformation are the main factors affecting the long-term stability and strength characteristics of rocks under hydro-mechanical coupling. Triaxial creep tests were performed on rock-like mortar specimens containing a pre-existing 3-D crack to investigate the time-dependent mechanical behavior of the cracked rock. A modified theoretical model for the irreversible deformation of rocks based on subcritical crack propagation was used to analyze the creep mechanism of the specimens and the effects of water pressure. The specimens with creep damage mainly exhibited a tensile-shear failure mode, and the macrofracture presented more tensile characteristics with increasing water pressure. The water pressure promoted the prefabricated crack propagation, inhibited the formation of microcracks, increased the creep rate, and accelerated specimen failure, which had a negative effect on the long-term stability of the specimens. The modified model accurately predicted the variation in irreversible axial strain and time required for specimen failure, especially under higher water pressures. The creep deformation of the specimens was much larger than the instantaneous deformation at the same crack propagation length, indicating that subcritical crack propagation is the main factor leading to the failure of rocks.