不同倾角厚层灰岩极限拉应变确定方法研究  

Study on ultimate tensile strain determining method of thick layered limestone with different dip angles

作　　者：刘博 左双英[1,2] 钟帅 陈世万 田娇[3] LIU Bo;ZUO Shuangying;ZHONG Shuai;CHEN Shiwan;TIAN Jiao(College of Resources and Environmental Engineering,Guizhou University,Guiyang 550025,China;Key Laboratory of Karst Geological Resources and Environment of Ministry of Education,Guizhou University,Guiyang 550025,China;Guizhou Provincial Transportation Planning Survey and Design Research Institute Co.,Ltd.,Guiyang 550081,China)

机构地区：[1]贵州大学资源与环境工程学院,贵州贵阳550025 [2]贵州大学喀斯特地质资源与环境教育部重点实验室,贵州贵阳550025 [3]贵州省交通规划勘察设计研究院股份有限公司,贵州贵阳550081

出　　处：《人民长江》2023年第3期190-199,共10页Yangtze River

基　　金：国家自然科学基金项目(42167025);贵州省科技重大专项计划(黔科合重大专项字[2018]3011);贵州省科学技术基金重点项目(黔科合基础[2020]1Z052)。

摘　　要：岩土工程中广泛应用极限分析法判断岩土体的局部破坏和整体破坏,其中极限应变值的确定是关键。基于室内试验、FLAC 3D有限差分和PFC 2D离散元方法,对7种不同倾角厚层灰岩岩样进行巴西劈裂试验及对应的数值模拟,研究其抗拉力学参数各向异性特征和破坏过程,并对3种确定极限拉应变的方法进行对比分析。研究结果表明:不同倾角的层状灰岩其抗拉强度和峰值应变具有各向异性特征;0~90°倾角岩样破坏模式从基质拉裂破坏逐渐向拉-剪复合破坏、层理拉裂破坏转变;应力-应变曲线弹性阶段的终点纵坐标为极限拉应变,其大小约为破坏拉应变的70%,当应变超过极限拉应变后裂纹开始萌生、扩展从而进入塑性阶段;3种方法得出的极限拉应变值随岩层倾角变化规律相似,量值差异较小。将室内试验和数值模拟相结合能从宏细观层面多角度展示含层理灰岩岩样裂纹萌生、扩展及贯通的全过程,对于岩土工程设计中的参数取值具有重要的指导意义。The limit analysis method is widely used in geotechnical engineering,which can be used to judge the local and overall failure of the rock and soil mass,so the determination of limit strain value is a key.Based on laboratory tests,FLAC 3D finite difference method and PFC 2D discrete element method,Brazilian splitting tests were carried out on seven types of thick layered limestone samples with different dip angles to study their anisotropic characteristics of tensile mechanical parameters and failure processes,and the results of three methods for determining ultimate tensile strains were compared and analyzed.The results show that the tensile strength and peak strain of layered limestone with different dip angles have anisotropic characteristics.The failure mode of rock samples with dip angles from 0°to 90°gradually changes from matrix tensile fracture to tensile-shear composite failure and bedding tensile fracture.The ordinate of the end point in the elastic stage of the stress-strain curve is determined as the ultimate tensile strain,which is about 70%of the tensile strain at failure,and when the strain exceeds the ultimate tensile strain,cracks begin to initiate and expand and entering a plastic stage.The ultimate tensile strain values obtained by the three methods have similar variation laws with the change of dip angle,and the magnitude difference is small.The combination of laboratory test and numerical simulation can show the whole process of crack initiation,extension and penetration of bedded limestone samples from a macroscopic level,which has important guiding significance for the parameter value selection in engineering design.

关 键 词：极限拉应变 层状岩体 各向异性 巴西劈裂试验 数值模拟 

分 类 号：TU446[建筑科学—岩土工程]