砂岩三轴卸荷路径下的力学特征及能量演化规律研究  

Mechanical characteristics and energy evolution of sandstone under triaxial unloading path

作　　者：李胤达 尚涛[1] 韩流[1] 陈树召[1] LI Yinda;SHANG Tao;HAN Liu;CHEN Shuzhao(School of Mines,China University of Mining and Technology,Xuzhou,Jiangsu 221116,China)

机构地区：[1]中国矿业大学矿业工程学院,江苏徐州221116

出　　处：《采矿与安全工程学报》2023年第3期621-632,共12页Journal of Mining & Safety Engineering

基　　金：国家重点研发计划项目(2016YFC0501103);国家自然科学基金青年基金项目(51804298);国家自然科学基金项目(51774271)。

摘　　要：为更准确地认识卸荷作用对岩石力学性质及裂隙发育过程的影响,开展了低损伤条件下卸围压常三轴试验,分析5种卸荷速率下试样的力学响应,基于弹塑性理论研究卸荷膨胀效应及径向能量演化规律。结果表明:不同路径卸载围压试验,轴向、径向应变经历了不同的变化阶段,试样呈现张剪复合破坏,卸荷路径增强了内摩擦效应;卸荷过程中,剪胀角呈现先快速增加并达到峰值,短暂保持后逐渐减小,最后趋于稳定的演化规律;径向体积功密度先线性减小,后加速减小直至岩样破坏。针对低损伤条件下砂岩试样,卸荷速率对其力学响应及能量演化影响较小,试样破坏机理为:围压卸载后,张拉裂隙发育,承载能力下降到卸荷阈值,压剪裂隙快速发育形成宏观裂纹,试样发生破坏。To more accurately understand the influence of unloading on the mechanical properties of rock and the process of fracture development,the constant triaxial test with confining pressure unloading under low damage conditions was carried out to analyze the mechanical response of the specimen under five unloading rates.Based on the elastic-plastic theory,the expansion effect of unloading and the evolution law of radial energy were studied.The results show that the axial and radial strains experience different stages of change in the confining pressure unloading tests with different paths,where the specimens show tensile-shear composite failure,and the unloading paths enhance the internal friction effect.In the process of unloading,the dilatancy angle increases rapidly to the peak,and then decreases gradually after a short period,and finally stabilizes.The radial volume work density decreases linearly first and then accelerates to decrease until the rock sample is destroyed.The unloading rate has little effect on the mechanical response and energy evolution of sandstone samples under low damage conditions.The failure mechanism of sandstone samples could be described as follows:after confining pressure unloading,tension cracks develop,the bearing capacity decreases to the unloading threshold,and the pressure shear cracks develop rapidly to form macroscopic cracks,and finally the sample is destroyed.

关 键 词：岩石力学 卸荷路径 卸荷速率 破坏模式 剪胀角 能量演化 

分 类 号：TD315[矿业工程—矿井建设]