Deep underground rock masses containing cross-fractures are highly susceptible to dynamic instability under water pressure within fractures, serving as a primary trigger for water inrush and collapse in underground engineering. This investigation employed an RMT system to conduct uniaxial compression tests, integrated with the combined finite-discrete element method (FDEM). A systematic study was carried out to elucidate the mechanisms by which water pressure within fractures influences the mechanical response and failure evolution of cross-fractured rock masses across varying persistence ratios of primary and secondary fractures. The results demonstrate that water pressure within fractures significantly reduces both the strength and stiffness of the rock mass (exhibiting a maximum reduction in peak strength of up to 35.3%) and accelerates the failure process. As the fractures persistence ratio (γ) increases, both the crack initiation stress and damage stress undergo nonlinear attenuation. When γ > 0.67, the stress reduction reaches 15%–30%. Under water pressure, the AE energy release transitions from a concentrated, burst-like pattern to a gradual and dispersed distribution. At a fully persistent fracture (γ = 1), the peak AE energy release decreases by 62.5% compared to the condition without water pressure. The synergistic effect of fracture water pressure and fracture geometry reconfigures both the stress–strain field and the hydro-mechanical field, driving a transition in the failure mode from a shear-tensile mixed mode to a fluid-pressure-dominated hydro-mechanical coupling mode. This study elucidates the coupled control exerted by water pressure and fracture geometry on the weakening mechanisms of fractured rock masses, thereby providing both experimental evidence and numerical validation for stability assessment of cross-fractured rock masses in deep underground engineering.Highlights<UnorderedList Mark="Bullet"> <ItemContent> The effect of cross-jointed fractures on the mechanical properties of rock masses under fissure water pressure was investigated. </ItemContent> <ItemContent> Based on the maximum tangential stress (MTS) criterion and acoustic emission signals, the evolution of crack initiation stress in rock masses under fissure water pressure was analyzed. </ItemContent> <ItemContent> An experimental scheme and numerical simulation method were developed to investigate the damage and failure behavior of cross-fractured rock masses under fissure water pressure. </ItemContent> </UnorderedList>

Study on Mechanical Properties and Crack Evolution Mechanism of Cross-Fractured Rock Mass Under Fissure Water Pressure

期刊论文
发表日期：

2025年11月14日

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Tingting Liu,
Lipan Cheng,
Fengwei Yang,
Runchao Yang,
Luyang Ding,
Lie Liu,
Xinping Li

摘要

Deep underground rock masses containing cross-fractures are highly susceptible to dynamic instability under water pressure within fractures, serving as a primary trigger for water inrush and collapse in underground engineering. This investigation employed an RMT system to conduct uniaxial compression tests, integrated with the combined finite-discrete element method (FDEM). A systematic study was carried out to elucidate the mechanisms by which water pressure within fractures influences the mechanical response and failure evolution of cross-fractured rock masses across varying persistence ratios of primary and secondary fractures. The results demonstrate that water pressure within fractures significantly reduces both the strength and stiffness of the rock mass (exhibiting a maximum reduction in peak strength of up to 35.3%) and accelerates the failure process. As the fractures persistence ratio (γ) increases, both the crack initiation stress and damage stress undergo nonlinear attenuation. When γ > 0.67, the stress reduction reaches 15%–30%. Under water pressure, the AE energy release transitions from a concentrated, burst-like pattern to a gradual and dispersed distribution. At a fully persistent fracture (γ = 1), the peak AE energy release decreases by 62.5% compared to the condition without water pressure. The synergistic effect of fracture water pressure and fracture geometry reconfigures both the stress–strain field and the hydro-mechanical field, driving a transition in the failure mode from a shear-tensile mixed mode to a fluid-pressure-dominated hydro-mechanical coupling mode. This study elucidates the coupled control exerted by water pressure and fracture geometry on the weakening mechanisms of fractured rock masses, thereby providing both experimental evidence and numerical validation for stability assessment of cross-fractured rock masses in deep underground engineering.

Highlights

The effect of cross-jointed fractures on the mechanical properties of rock masses under fissure water pressure was investigated.

Based on the maximum tangential stress (MTS) criterion and acoustic emission signals, the evolution of crack initiation stress in rock masses under fissure water pressure was analyzed.

An experimental scheme and numerical simulation method were developed to investigate the damage and failure behavior of cross-fractured rock masses under fissure water pressure.