不同初始卸荷水平下红砂岩波速变化及能量耗散规律试验研究  

Experimental study on wave velocity variation and energy dissipation law of red sandstone under different initial unloading levels

作　　者：张培森[1,2] 赵成业 侯季群 张睿[1,2] 李昊[1,2] ZHANG Peisen;ZHAO Chengye;HOU Jiqun;ZHANG Rui;LI Hao(National Key Laboratory for Mine Disaster Prevention and Control,Shandong University of Science and Technology,Qingdao 266590,China;National Demonstration Center for Experimental Mining Engineering Education,Shandong University of Science and Technology,Qingdao 266590,China)

机构地区：[1]山东科技大学矿山灾害预防控制国家重点实验室培育基地,山东青岛266590 [2]山东科技大学矿业工程国家级实验教学示范中心,山东青岛266590

出　　处：《煤炭学报》2021年第S01期157-173,共17页Journal of China Coal Society

基　　金：国家重点研发计划资助项目(2018YFC0604702);国家自然科学基金资助项目(51379119);山东省重点研发计划资助项目(2018GSF120009)。

摘　　要：为研究红砂岩在不同初始卸荷水平(初始应力差水平与岩石对应围压条件下峰值强度的比率)下的波速变化及能量耗散规律,利用Rock Top多场耦合试验仪和JSR-DPR300超声测试系统,在同一围压条件下,开展三轴加载路径、应力差恒定卸围压与应力差增大卸围压2种卸荷路径、3个初始卸荷水平下的红砂岩应力-应变过程中的纵、横波速测试试验。研究结果表明:围压加载过程中,纵、横波速均随围压的增大而增大,呈幂函数关系;孔隙度、密度随着围压的升高,对围压的敏感性降低,变化幅度减小;岩石内部不同类型的孔隙其闭合的应力阈值不同,波速受控于岩石的密实程度与岩石骨架性质。围压卸荷过程中,在不同卸荷路径下,随着初始卸荷水平的增大,极限应变增大,统一围压降参数均呈线性降低,应变围压增量比呈幂函数增大,环向变形对围压变形更为敏感,相较于卸荷路径的影响,初始卸荷水平对岩石卸荷变形过程具有控制作用;不同初始卸荷水平下,纵、横波速随轴向应变的变化曲线同应力-应变曲线基本对应,反映了岩样不同的劣化水平,纵、横波速各自整体上的增长衰减趋势具有一致性,卸荷路径对波速的影响较弱,在加载和卸荷2个区间内存在明显的阶段性特征,波速在卸荷起始点迎来大幅度偏转,纵波以此分为增长阶段和衰减阶段,横波分为稳定阶段和衰减阶段,纵波对轴向压力更为敏感,震荡性强烈。围压卸荷伊始,岩石由压缩迅速转为扩容或扩容加剧,应变能密度在卸荷起始点及应力跌落点迎来一次、二次偏转,后者偏转幅度远小于前者;应力差恒定卸围压过程中,弹性应变能近似稳定,其增长趋势和轴向应力-应变曲线是一致的,即轴向应力做功是其主要能量补充方式;能量的耗散集中在卸荷区间内,卸荷前期稳定增长,卸荷后期急速增长,弹性能的释放集中在应力跌落�In order to study the law of wave velocity variation and the energy dissipation of red sandstone under different initial unloading levels(initial differential stress level and the corresponding ratio of the peak intensity under the condition of confining pressure of rock),using Rock Top several coupling tester and JSR-DPR300 ul-trasonic testing system,at the same confining pressure conditions,the compression and shear wave velocities in the stress-strain process of red sandstone under the three initial unloading levels were tested,which were in the triaxial loading path and unloading path of stress difference constant release confining pressure and stress difference increase release confining pressure.The results show that in the process of confining pressure loading,the compression and shear wave velocities increase with the increase of confining pressure,showing a power function relationship.With the increase of confining pressure,the sensitivity of porosity and density to confining pressure and the range of variation decrease.The stress threshold for the closure of different types of pores in the rock is different,and the wave velocity is controlled by the degree of compaction of the rock and the nature of the rock skeleton.In the process of confining pressure unloading,under different unloading paths,with the increase of the initial unloading,the ultimate strain increases,uniform confining pressure drop parameters linearly reduces,strain confining pressure increment ratio increases in power function,circumferential deformation of confining pressure is more sensitive,compared with unloading paths,the influence of the initial unloading level plays an control role in rock unloading deformation process.Under different initial unloading levels,the curves of compression and shear wave velocities with axial strain are corresponded to the stress-strain curves,reflecting the different degradation levels of rock samples,the overall growth and attenuation trends of compression and shear wave velocities are consistent.Th

关 键 词：初始卸荷水平 卸围压 纵波 横波 能量演化 

分 类 号：TD315[矿业工程—矿井建设]