锦屏大理岩力学特性试验及其数值模拟

采用锦屏大理岩进行三轴压缩过程中力学特性室内试验,并从岩石细观力学角度对其力学特性成因进行探讨。在此基础上通过引入两个参数,进一步建立了能够反映大理岩全应力-应变过程中强度变形特性的黏聚力弱化-摩擦角强化(CWFS)改进模型,并采用试验结果对该模型进行验证。研究结果表明:(1)随着围压的增大,锦屏大理岩表现出明显的脆-延-塑性转换的峰后力学特性,峰值强度与残余强度之间的差值呈单调减小的趋势,应力-应变曲线中由峰值强度向残余强度跌落段曲线的斜率逐渐变缓;(2)高围压条件下岩石裂隙之间的摩擦力、岩石内部材料的均匀化程度是导致大理岩表现出脆-延-塑性转换的峰后力学特性的主要原因;(3)黏聚力弱化-摩擦角强化改进模型能较好地描述大理岩全应力-应变过程的强度、变形特征,且模型参数物理意义明确,易于获得。

Experimental study on mechanical behaviors of Jinping marble and its numerical modeling

Laboratory tests were conducted to study the mechanical behaviors of Jinping marble during triaxial compression process. From the perspective of micromechanics, the genesis of its mechanical characteristics is discussed. On this basis, by introducing two factors, the modified CWFS model was established, which could reflect the cohesion weakening and friction strengthening characteristics of marble during the stress-strain process. Subsequently, the modified CWFS model was validated by test results. The results showed that: ① with the increase of confining pressure, obvious post-peak brittle-ductile-plastic transition of Jinping marble was demonstrated, the difference between peak strength and residual strength decreased monotonously, and the slopes of stress-strain curves become gentle from peak strength falling to residual strength;② under high confining pressures, the friction between rock fractures and the inside homogenization degree of rock were the main causes leading to post-peak brittle-ductile-plastic transition of marble;③ the modified CWFS model could reasonably describe the strength and deformation characteristics of marble during the whole stress-strain process, and the physical meanings of model parameters are explicit and were easy to be obtained.