摘要
Mohr-Coulomb模型和基于Mohr-Coulomb的应变软化模型均通常假设剪胀角为恒定值,然而这种假设不能正确表达岩石在破坏变形过程中的非线性体积变化行为。根据7种岩石类型在不同围压条件下的体积应变测量数据,结合塑性力学理论,采用非线性拟合方法建立能同时考虑围压和塑性剪切应变影响的剪胀角模型。分析模型的响应并结合岩石内部颗粒尺寸以及单轴抗压强度,将该模型划分为4种岩石类型:粗粒径硬岩、中粒径硬岩、中–细粒径软岩和细粒径软岩。根据FLAC应变软化模型中非关联塑性流动法则的计算原理,推导剪胀角模型中的塑性剪切应变与应变软化模型中塑性参数的关系,将剪胀角模型嵌入应变软化模型中,构建剪胀角模型模块。最后,采用建立的剪胀角模型预测Moura煤岩在三轴压缩条件下的体积应变–轴向应变关系曲线。研究结果表明,数值模拟与试验结果具有很好的一致性。
Conventional Mohr-Coulomb model and strain-softening based Mohr-Coulomb model often take an assumption of constant dilation angle,which can not be supported by experimental data,and it is observed that the approach is not successful in characterizing the nonlinear deformation behaviors of rocks. Based on published data acquired from modified triaxial compressive tests with volumetric strain measurement performed on seven types of rocks,a mobilized dilation angle model which considers both confining stress and plastic shear strain is developed. Based on the model response and in combination with the grain size description and the uniaxial compressive strength of the seven types of rocks,the model is generalized for four rock types：coarse-grained hard rock,medium-grained hard rock,fine-medium-grained soft rock,and fine-grained soft rock. According to the principle of nonassociated flow rule in the strain-softening models in FLAC,the relationship between the plastic shear strain in the proposed dilation angle model and characteristic plastic parameter in strain-softening model is deduced;and the proposed dilation angle model is implemented in FLAC using FISH language. The dilation angle model is used to predict the volumetric-axial strain relationships of Moura coal;and the results are found to be in good agreement with experimental results. Finally,the importance of using the confinement and plastic shear strain dependent dilation angle model for rock engineering applications is discussed.
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2010年第5期970-981,共12页
Chinese Journal of Rock Mechanics and Engineering
基金
国家留学基金资助项目(国家建设高水平大学公派研究生项目)
关键词
岩石力学
岩石扩容
剪胀角模型
围压
塑性剪切应变
数值模拟
rock mechanics
rock dilation
dilation angle model
confining stress
plastic shear strain
numerical s imulation
