峰后脆性对非均质岩石试样破坏及全部变形的影响  

Effects of post-peak brittleness on failure and overall deformational characteristics of rock specimen with random material imperfections

作　　者：王学滨[1] 

机构地区：[1]辽宁工程技术大学力学与工程科学系,辽宁阜新123000

出　　处：《中南大学学报（自然科学版）》2008年第5期1105-1111,共7页Journal of Central South University:Science and Technology

基　　金：国家自然科学基金资助项目(50309004)

摘　　要：在平面应变压缩条件下,采用FLAC模拟峰后脆性对含初始随机材料缺陷的岩样的破坏过程、前兆、声发射及全部变形特征的影响。利用若干FISH函数预置初始随机缺陷,计算全部变形特征,并统计每10个时间步内的破坏单元数。密实的岩石服从莫尔库仑剪破坏与拉破坏复合的破坏准则,破坏之后呈现应变软化-理想塑性行为。缺陷在破坏之后经历理想塑性行为。不同脆性岩石的峰后的应力-轴向应变曲线、应力-侧向应变曲线、侧向应变-轴向应变曲线、体积应变-轴向应变曲线及由侧向应变及轴向应变计算得到的泊松比-轴向应变曲线于应力峰值之前发生分离。由于缺陷的依次破坏,在初始加载阶段之后,计算得到的泊松比随着轴向应变的增加而直线上升,这使侧向应变增加的速度超过轴向应变增加的速度。随着峰后脆性的降低,岩样失稳破坏的前兆变得明显,破坏变得不突然。脆性越强的材料,体积膨胀之后发生应变软化越早;剪切应变集中的位置越少;在硬化阶段及软化阶段,声发射持续的时间越短。In uniaxial plane strain compression, the failure processes, precursors, acoustic emissions and overall deformational characteristics of rock specimens with initially random material imperfections were modeled using FLAC. FISH functions were used to generate initial imperfections, calculate overall deformational characteristics and to remember the number of failed elements per 10 timesteps. For intact rock element exhibiting linear strain-softening behavior after the occurrence of failure and then ideal plastic behavior, the failure criterion is a composite Mohr-Coulomb criterion with tension cut-off. Initial imperfections undergo ideal plastic behavior after the occurrence of failure. At different post-brittleness, the stress-axial strain curve, stress-lateral strain curve, lateral strain-axial strain curve, volumetric strain-axial strain curve and calculated Poisson＇s ratio-axial strain curve separate prior to the peak stress. After the initially loading stage, the calculated Poisson＇s ratio linearly increases with axial strain since material imperfections fail progressively so that the increase in the lateral strain exceeds the increase in the axial strain. As post-brittleness decreases, precursors to failure tend to be apparent and failure processes become less sudden. For more brittle rock, strain-softening behavior occurs earlier after the volume dilation; shear strain concentration zones are fewer and the acoustic emission duration in strain-hardening and strain-softening stages is longer.

关 键 词：非均质性 材料缺陷 峰后脆性 剪切带 轴向应变 侧向应变 体积应变 前兆 

分 类 号：TU451[建筑科学—岩土工程]