大理岩脆-延-塑转换特性的细观模拟研究

MESOSCOPIC SIMULATION STUDY OF BRITTLE-DUCTILE-PLASTIC TRANSITION CHARACTER OF MARBLE

针对锦屏深埋大理岩峰后变形破坏的脆-延-塑转换特性,采用颗粒流程序(PFC)中的簇单元模型(CPM)对其进行细观模拟研究。经过对室内试验结果的反复模拟校准,获得描述锦屏深埋大理岩力学性质的一组细观物理力学性质参数。模型试验结果表明:试样的一系列宏观力学表现,包括弹性模量、泊松比、单轴与启裂抗压强度、应力-应变曲线、峰值与残余强度包络线、拉压强度比以及破坏形态等均与锦屏深埋大理岩的试验结果具有良好的一致性。对不同围压下裂纹发育规律的研究表明:不同应力状态下细观裂纹发育特征的显著差异是导致大理岩的变形破坏出现脆-延-塑转换特性的主要原因;张性裂纹的大量发育决定介质的脆性破坏模式,而剪切裂纹数目的快速增长则促使介质由脆性破坏模式逐渐向延-塑性破坏模式转换。

The deformation and failure characteristics of brittle-ductile-plastic transition,which is shown in the post-peak stage for Jinping deep marble,was simulated by clumped-particle model（CPM） of particle flow code（PFC）,and studied from the micro view.After a long process of trial-and-error calibration of laboratory test results,a set of micro parameters for Jinping deep marble were obtained.It is shown that a series of macroscopic mechanical properties of the synthetic rock,including the elastic modulus,Poisson＇s ratio,uniaxial compressive and crack initiation strengths,stress-strain curves,the peak and residual strength envelops,the ratio of tensile to uniaxial compressive strength,and the failure patterns of synthetic rock samples,all agree well with the test results of Jinping deep marble.Study of regularities of crack development in synthetic rock samples at different confining pressures indicates that：The significant difference of development features of microcracks at different confining pressures is the main reason which leads to Jinping deep marble appearing brittle-ductile-plastic transition character;and the development of large number of tension cracks determines the brittle failure pattern of medium,while the rapid growth of shear cracks prompts the failure patterns of medium transition from brittle to ductile or plastic.