孔洞裂隙砂岩声发射特性与能量演化过程的多尺度关联性分析
Multi-scale correlation analysis of acoustic emission characteristics and energy evolution process of cavernous fractured sandstone
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摘要: 为探究不同孔洞、裂隙下砂岩受载断裂失稳的力学特性、能量演化及声发射特征, 对临沂山区红砂岩试样开展了不同孔洞直径、裂隙倾角条件下的单轴压缩试验, 基于最小能量理论和坚固体假说, 分析不同试件应力−应变曲线、能量演化规律及声发射特征。研究表明: 裂隙扩展贯通会导致砂岩失稳破坏, 不同孔洞直径、裂隙倾角下砂岩体力学性质不同。砂岩的应力随裂隙倾角先降后升, 孔洞直径增大使应力降低, 但降幅小; 应变随裂隙倾角呈现“M”型变化。砂岩应变能随加载过程呈现慢增、快增、峰后稳定规律, 裂隙增大时应变能先降后升。砂岩加载时声发射能量断续增长, 达到应力峰值前有“平静期”现象, 破坏后声发射能量最大, 声发射能量与应变能呈幂函数关系。提出了裂隙岩体扰动失稳破坏的假说, 坚固体断裂后, 扰动导致自组织临界状态的砂岩失稳破坏, 并通过声发射定位和实际裂隙扩展规律进行了验证。研究成果对于裂隙砂岩的稳定性监测预警及灾害防治具有重要的理论意义与实用价值。Abstract: To investigate the load-induced fracture instability of cavernous fractured sandstone under varying hole diameters and fracture dips, uniaxial compression tests were performed on red sandstone samples from the Linyi mountainous area. Based on the minimum energy theory and the hard body hypothesis, the stress-strain curves, energy evolution laws, and AE characteristics of different specimens were analyzed. The results show that fracture propagation and coalescence lead to the instability and failure of sandstone, and the mechanical properties of the sandstone differ with varying hole diameters and fracture dip angles. The stress of sandstone first decreases and then increases with the fracture dip angle. An increase in hole diameter reduces the stress, but the magnitude of reduction is small. The strain exhibits an "M"-shaped variation pattern with the fracture dip angle. The strain energy of sandstone during loading shows a pattern of slow increase, rapid increase, and post-peak stability. With the increase of fracture size, the strain energy first decreases and then increases. The AE energy during sandstone loading increases intermittently, and a "quiet period" phenomenon is observed before reaching the peak stress. The AE energy is greatest after failure. The relationship between AE energy and strain energy follows a power function. A hypothesis for the disturbance-induced instability failure of fractured rock masses was proposed: after the fracture of the hard body, disturbance leads to the instability failure of sandstone in a self-organized critical state. This was validated through AE localization and the actual fracture propagation patterns. The research findings hold significant theoretical and practical value for stability monitoring, early warning, and disaster prevention and control in fissured sandstone.