多孔弱胶结岩石破裂的围压影响机制及压密-损伤本构模型  

Effects of confining pressure on failure mechanism of porous and weakly cemented rock and compaction-damage constitutive model

作　　者：苗胜军[1,2] 杨鹏锦 黄正均[1,2] 王辉 梁明纯[1,2] MIAO Shengjun;YANG Pengjin;HUANG Zhengjun;WANG Hui;LIANG Mingchun(Beijing Key Laboratory of Urban Underground Space Engineeing,University of Science and Technology Beijing,Beijing 100083,China;Civil and Resource Engineering School,University of Science and Technology Beijing,Beijing 100083,China)

机构地区：[1]北京科技大学城市地下空间工程北京市重点实验室,北京100083 [2]北京科技大学土木与资源工程学院,北京100083

出　　处：《中国矿业大学学报》2023年第2期229-240,共12页Journal of China University of Mining & Technology

基　　金：国家自然科学基金项目(51974014,U2034206,51574014)。

摘　　要：通过开展粉砂岩单轴、三轴压缩试验,研究不同围压下岩石的力学性质及声发射活动规律,揭示了围压对多孔弱胶结岩石破裂的影响机制;根据声发射能量计数建立损伤变量,并提出了表征岩石损伤分布程度的损伤度;采用粉砂岩空隙体积应变建立岩石的空隙压密度,验证岩石空隙压密-损伤破裂本构模型并进行了参数分析.研究表明:1)施加围压阶段产生的体积压缩量最高,占据岩石最大体积压缩量的65%;泊松比随围压增大而减小,与致密硬岩恰好相反.2)围压限制了岩石的微裂纹扩展,粉砂岩单轴压缩时的声发射振铃计数率最大值为三轴压缩的十几倍;围压越大,声发射空间分形维数越小,微裂纹分布越集中.3)多孔弱胶结岩石的破坏是岩石内部短时间内产生大量小尺度剪切微破裂并迅速汇集—兼并形成大尺度宏观裂纹的过程;低围压可以有效地抑制小尺度微裂纹的扩展,而高围压对大尺度微裂纹的约束效果更明显.4)空隙压密-损伤破裂本构模型的理论参数物理意义清晰,能够准确反映围压对粉砂岩压密及破坏的影响机制,对于描述三轴压缩下多孔弱胶结岩石变形破坏规律具有较好的适用性.The uniaxial and triaxial compression tests were conducted to investigate the mechanical characteristics,acoustic emission(AE) activity of rock,the effect of confining pressure on failure mechanism of porous weakly cemented rock was revealed. According to the AE energy count,the damage variable was established,and the damage degree of rock damage distribution was proposed. The void pressure density of rock was established by using the void volume strain of siltstone,and the constitutive model of rock void compaction-damage fracture was verified and the parameters were analyzed. The results show that: 1) The volume compression produced in the confining pressure stage is the highest,accounting for 65% of the maximum volume compression of rock. Poisson’s ratio decreases with the increase of confining pressure,which is just opposite to that of dense hard rock. 2) Confining pressure can limit the crack propagation of rock,the maximum AE ring count of siltstone under uniaxial compression is more than ten times that under triaxial compression. With the increase of confining pressure,the spatial fractal dimension of AE decreases and the cracks distribution are more concentrated.3) The failure of porous weakly cemented rock is a process in which a large number of small-scale shear micro-fractures are generated in a short period of time in the rock and quickly converge and then merge to form large-scale macro-cracks. Low confining pressure can effectively inhibit the propagation of small-scale microcracks,while high confining pressure has a more obvious constraint effect on large-scale microcracks.4) The theoretical parameters of the void compaction-damage fracture constitutive model have clear physical meaning,which can accurately reflect the influence mechanism of confining pressure on the compaction and failure of siltstone. It has good applicability for describing the deformation and failure law of porous weakly cemented rock under triaxial compression.

关 键 词：多孔弱胶结岩石 声发射b值 围压 破裂机制 本构模型 

分 类 号：TU45[建筑科学—岩土工程]