Mechanical properties, failure behaviors and permeability evolutions of fissured rock-like materials under coupled hydro-mechanical unloading

Abstract

This work aims to experimentally investigate the failure mechanism and the spatiotemporal evolution of permeability in the fissured rock-like specimens under the coupled hydromechanical conditions. The different factors on the coupled hydromechanical loading/unloading failure mechanism are investigated. The experimental results of 3-D internal fracture morphology obtained from the X-ray CT scanning system coupled with 3-D reconstruction techniques indicate that the initial unloading state promotes the nucleation of the secondary cracks at the low internal hydraulic pressures. The nucleation of secondary cracks is inhibited when the hydraulic pressure of the fluid-injection is high. Furthermore, the quantitative relationships among the 3-D fractal dimensions, mechanical strengths and permeability are constructed to discover the coupled hydromechanical unloading failure mechanism. The coupled hydromechanical prepeak unloading failure mechanism summarized in this work provides the deep insights in the underground engineering.