Mechanistic effects of initial damage on the degradation of sandstone mechanical properties
YAN Qixiang1, HE Wencheng1, LIU Ruiqi1, SUN Minghui1, 2*, YANG Xiao3
(1. State Key Laboratory of Intelligent Geotechnics and Tunnelling, Southwest Jiaotong University, Chengdu, Sichuan 610031, China; 2. School of Civil and Hydraulic Engineering, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China; 3. China Power Construction Chongqing Survey and Design Institute, Chongqing 401329, China)
Abstract：Deep underground excavation inevitably induces varying degrees of initial damage to the surrounding rock, significantly altering its load-bearing capacity and deformation behavior. However, conventional strength criteria are insufficient for quantitatively characterizing these damage effects. This study aims to elucidate the deterioration mechanisms of sandstone under initial damage and to develop an improved strength criterion suitable for engineering predictions. Sandstone specimens with varying levels of damage were prepared through uniaxial incremental cyclic loading-unloading tests, from which their peak strength, deformation modulus, and shear strength parameters were obtained via triaxial compression tests. Additionally, PFC2D was utilized to simulate crack initiation, propagation, and coalescence, providing microscopic insights into the damage-induced weakening of strength. Based on these findings, the staged influence of damage on the Hoek-Brown parameters m and s was quantified, leading to the establishment of a “damage-parameter” relationship incorporated into the generalized Hoek-Brown criterion, thereby enhancing the strength prediction method. The results indicate that initial damage causes exponential decay in peak strength and stiffness, accompanied by an increase in Poisson′s ratio, with the damage effect being strongly dependent on confining pressure. The reconstruction and weakening of the crack network were identified as fundamental causes of macroscopic deterioration, while high confining pressure effectively suppresses tensile cracking and promotes frictional slip, thereby delaying failure. The improved Hoek-Brown criterion accurately captures strength reduction at different damage levels. Engineering case verification further demonstrates that the proposed method yields higher prediction accuracy for surrounding rock deformation compared to conventional criteria. This study provides a quantitative approach for evaluating strength degradation in excavation-induced damaged rock and offers valuable guidance for stability assessment and support optimization in deep underground engineering.
晏启祥1，贺文城1，刘瑞琦1，孙明辉1，2*，杨 潇3. 初始损伤对砂岩力学性能劣化的影响机制研究[J]. 岩石力学与工程学报, 2026, 45(5): 1378-1391.
YAN Qixiang1, HE Wencheng1, LIU Ruiqi1, SUN Minghui1, 2*, YANG Xiao3. Mechanistic effects of initial damage on the degradation of sandstone mechanical properties. , 2026, 45(5): 1378-1391.
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2026, Vol. 45 
