Hydraulic properties and energy dissipation of deep hard rock under H-M coupling and cycling loads

Abstract

The permeability of deep rock is closely related to the stability and safety of underground engineering. The rocks in deep stratum are mostly with high stress and high osmotic pressure. Therefore, it is necessary to consider the coupling effect between porewater pressure and in situ stress on rock mass. A series of triaxial cyclic loading and unloading experiments under hydraulic-mechanics coupling conditions are carried out to studied the mechanical and hydraulic properties of granite in the depth of 1300 m to 1500 m. Especially, the effect of the disturbance on the permeability of fractured rocks are investigated by unloaded the confining pressure. Tests results presented that the stress-strain curves of deep granite showed typical brittle characteristics. The principal stress of granite exhibited a linear relationship under the high confining pressure of 34-40 MPa and high osmotic pressure of 13-15 MPa. Dissipated energy of the rock decreased to a relatively low level after 2-3 loading cycles and then slowly increased. Permeability showed a decreasing trend as the loading and unloading cycles increase. Finally, acoustic emission technology was used to monitor the fracture evolution in rocks, the acoustic emission signal released as the fractures develop and energy dissipated. The results would provide basic data for the exploitation and excavation in the deep galleries.

Experimental investigation on the evolution of damage and seepage characteristics for red sandstone under thermal–mechanical coupling conditions

“…Li et al (2017) studied the relationship between the seepage flow rate of rock fractures and temperature, and the results showed that the rock fracture opening and seepage flow rate gradually increased with the thermal temperature. Zhang et al (2019) found that the permeability of granite after losing its bearing capacity showed an exponential upward trend as the confining pressure decreased. After heat treatment, the permeability under the triaxial loading process first decreases in the micro-crack closure area, while it is almost constant in the elastic area, and then increases sharply in the crack propagation area (Chen et al 2014).…”

Permeability Evolution and Damage Characterization of Sandstone under Various Confining Pressures and Seepage Pressure Gradients

“…Numerous researchers have conducted triaxial hydromechanical coupling tests on different types of rocks to analyze their mechanical properties and permeability characteristics under various levels of confining and seepage pressures (Liu et al 2012;Zhao et al 2017;Oda et al 2002). Investigations into the relationship between permeability and confining pressure as well as seepage pressure have also been undertaken (Meng et al 2019;Zhang et al 2019). It is well established that the germination, extension, and connection of microfractures during the damage process are closely intertwined with rock permeability Liu et al 2018;Tan et al 2019;Wang et al 2013).…”

Study on Acoustic Emission Characteristics of Different Felsic Metagabbros Under Hydraulic Coupling

“…Zhang et al (2020a, b, c) conducted triaxial compression permeability experiments on sandstone using a rock top multi-field coupled tester to reveal the permeability law of rocks during the stress-strain process. Zhang et al (2019b) discovered that after the loss of bearing capacity, the permeability of granite increased exponentially with decreasing surrounding pressure. Wang et al (2018) analyzed the energy evolution law and permeability characteristics of deep coal rock by triaxial cyclic loading and unloading tests.…”