DENG Yun-chen;LUO Yi;XU TAO;LI Xin-ping;QU Deng-xing;HUA Guo-wei;School of Civil Engineering and Architecture, Wuhan University of Technology;Sanya Science and Education Innovation Park, Wuhan University of Technology;To thoroughly investigate the long-term stability and failure mechanisms of sandstone with initial damage under complex stress conditions, and to offer insights for the safe design and construction of deep rock engineering projects, this study conducted a systematic examination of the creep mechanical properties of damaged sandstone through comprehensive experimental analyses.The experimental methodology comprised three stages.Initially, a Split Hopkinson Pressure Bar(SHPB) system was utilized to generate sandstone specimens with three distinct levels of initial damage(D_1、D_2、D_3) by precisely regulating the impact air pressure.This dynamic loading process induced controlled distributions of micro-cracks within the rock matrix, thereby simulating realistic damage scenarios encountered in engineering applications.Secondly, conventional triaxial compression tests were carried out to determine the fundamental mechanical properties of both intact and damaged specimens across a range of confining pressures.Thirdly, systematic triaxial creep tests were conducted using a fully automated rock triaxial testing apparatus, applying three different confining pressure levels(5 MPa, 10 MPa, and 20 MPa).The creep tests followed a step-loading procedure, wherein each stress level was sustained for 4 hours or until specimen failure occurred, while continuous monitoring of axial strain development was used to fully capture the creep behavior.The experimental results reveal several pivotal observations.Notably, the creep stress level exerts a substantial influence on both the instantaneous strain and creep strain of damaged sandstone, and it governs the degree to which initial damage impacts the creep behavior of sandstone.A stress threshold σ_c was identified, below which the instantaneous strain increases linearly with creep stress, whereas above this threshold, the growth rate accelerates nonlinearly.This critical threshold value rises progressively with increasing confining pressure.The steady-state creep rate of damaged sandstone demonstrates exponential growth patterns as creep stress increases, remaining modest under low stress conditions but escalating rapidly under high stress levels.Initial damage significantly influences steady-state creep rate only under higher stress conditions, whereas its impact diminishes considerably as confining pressure increases.Quantitative analysis reveals that the creep failure stress decreases linearly with increasing initial damage degree, but increases dramatically with rising confining pressure.Under different confining pressure conditions, the creep failure stress ranges from 67.4% to 94.5% of peak strength, providing essential quantitative parameters for engineering applications.Failure mode analysis elucidates that the complexity of failure patterns is collectively determined by confining pressure and damage degree, with confining pressure exerting a dominant influence.Specimens under low confining pressure exhibit composite failure modes, characterized by a combination of shearing and splitting mechanisms, accompanied by extensive crack propagation.Conversely, under high confining pressure, failure predominantly manifests as simple shear failure with minimal crack formation.Notably, confining pressure exhibits a marked weakening of the initial damage′s impact on failure modes.The research findings illuminate the underlying mechanisms driving creep failure in damaged rocks and establish essential relationships between initial damage, stress conditions, and long-term mechanical behavior.These results provide vital theoretical foundations and technical support for assessing the long-term stability of damaged rock masses in deep tunnels, slope engineering, mining operations, and other critical infrastructure projects, as well as optimizing support parameters and developing early warning systems.
2025 04 v.42;No.178 [Abstract][OnlineView][Download 2438K]