Rock discontinuities critically influence the stability of mining tunnels and underground engineering caverns. While traditional studies have mainly examined the effect of normal stress on rock discontinuities via direct shear tests, real-world deep underground environments subject these discontinuities to high true three-dimensional (3D) stresses, including significant lateral stress (σp), however, the effect of σp on the shear behavior and cracking evolution of rock discontinuities under 3D stress conditions remains insufficiently studied. Therefore, a series of true triaxial disturbance shear tests (TTDST) were conducted on granite specimens containing a prefabricated discontinuity under different σp conditions using a novel self-developed true triaxial disturbance shear apparatus equipped with an acoustic emission (AE) system. The testing method was designed to simulate excavation-induced 3D stress redistribution. The influence of σp on the mechanical behavior, damage evolution, and AE response of specimens containing a prefabricated discontinuity was investigated, including disturbance shear deformation, strength characteristics, and the failure surface morphology characteristics. As σp increases, the disturbance critical shear strength exhibits a rise at first, then drops, and eventually stabilizes, with a maximum increment of 15% and a maximum decrement of 26%. The roughness of rock discontinuities follows a similar trend. During the critical failure, disturbance damage exhibits an S-shaped evolution, whereas the disturbance strain rate generally shows an accelerated pre-failure increase and, in some cases, a pronounced V-shaped trend. Low-energy, dispersed AE events predominate early in the shear process, while high-energy events cluster near discontinuities as failure approaches. Micro-cracking mechanisms are identified as tensile-shear mixtures, with the proportion of micro-shear cracks rising during shear failure and micro-tensile cracks overall increasing with higher σp. The failure precursors of rock discontinuities under TTDST are remarkable: the AE signal activity significantly intensifies, accompanied by substantial high-amplitude hits occurs in the medium–low frequency region; the fractal dimension increases suddenly, and the b-value drastically decreases to below 1, while lg N/b swiftly increases to above 4.

Effect of Lateral Stress on Disturbance Shear Cracking Evolution Mechanisms of Rock Discontinuities Under True Triaxial Shear Test

期刊论文
发表日期：

2026年6月3日

查看全文

Zhi Zheng,
Jiaju Zhou,
Houquan Zhang,
Bin Deng,
Tiejun Tao,
Fengyun Wang,
Rui Pan

摘要

Rock discontinuities critically influence the stability of mining tunnels and underground engineering caverns. While traditional studies have mainly examined the effect of normal stress on rock discontinuities via direct shear tests, real-world deep underground environments subject these discontinuities to high true three-dimensional (3D) stresses, including significant lateral stress (σ_p), however, the effect of σ_p on the shear behavior and cracking evolution of rock discontinuities under 3D stress conditions remains insufficiently studied. Therefore, a series of true triaxial disturbance shear tests (TTDST) were conducted on granite specimens containing a prefabricated discontinuity under different σ_p conditions using a novel self-developed true triaxial disturbance shear apparatus equipped with an acoustic emission (AE) system. The testing method was designed to simulate excavation-induced 3D stress redistribution. The influence of σ_p on the mechanical behavior, damage evolution, and AE response of specimens containing a prefabricated discontinuity was investigated, including disturbance shear deformation, strength characteristics, and the failure surface morphology characteristics. As σ_p increases, the disturbance critical shear strength exhibits a rise at first, then drops, and eventually stabilizes, with a maximum increment of 15% and a maximum decrement of 26%. The roughness of rock discontinuities follows a similar trend. During the critical failure, disturbance damage exhibits an S-shaped evolution, whereas the disturbance strain rate generally shows an accelerated pre-failure increase and, in some cases, a pronounced V-shaped trend. Low-energy, dispersed AE events predominate early in the shear process, while high-energy events cluster near discontinuities as failure approaches. Micro-cracking mechanisms are identified as tensile-shear mixtures, with the proportion of micro-shear cracks rising during shear failure and micro-tensile cracks overall increasing with higher σ_p. The failure precursors of rock discontinuities under TTDST are remarkable: the AE signal activity significantly intensifies, accompanied by substantial high-amplitude hits occurs in the medium–low frequency region; the fractal dimension increases suddenly, and the b-value drastically decreases to below 1, while lg N/b swiftly increases to above 4.