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剪胀角是描述岩石体积膨胀扩容的常用参数,在非关联流动法则中,连续介质理论通常假设剪胀角为0;在关联流动法则中,其值恒定且等于内摩擦角。岩石三轴压缩全过程体应变曲线表明,其体积剪胀性依赖于围压和塑性参量,破坏过程中不仅其特征强度随围压和塑性参量呈非线性变化,而且剪胀特性也表现出非线性特征。基于塑性力学理论,针对锦屏大理岩损伤控制的全过程三轴加、卸载试验,采用双参数非线性函数拟合方法建立了能同时考虑围压效应和塑性参量的非线性剪胀角模型。结果表明,对于大理岩、中硬岩,在破坏过程中扩容行为强烈依赖围压和岩石塑性参量,均表现出先快速增加至峰值后,随着塑性变形增加逐渐减小的非线性演化规律。提出的双参数非线性剪胀角模型很好地描述了岩石破坏过程中的体积扩容特性,其结果对于研究地下工程围岩应力变化诱发的围岩剪胀破坏机制、体积扩容膨胀区范围预测和围岩支护的合理设计均具有一定的理论和工程应用价值。
The dilatancy angle is a commonly used parameter to describe the volume expansion and expansion of rocks. In the non-associated flow law, the continuous medium theory usually assumes that the dilatancy angle is 0; in the associated flow law, it is constant and equal to the internal friction angle. The whole body strain curve of rock triaxial compression shows that the volume dilatancy depends on the confining pressure and plasticity parameters. During the failure process, not only the characteristic strength nonlinearly changes with the confining pressure and plasticity parameters, but also the dilatancy characteristics Linear features. Based on the theory of plastic mechanics, a nonlinear dilatancy angle model considering the confining pressure effect and plasticity parameters was established for the entire process of triaxial loading and unloading tests for the damage control of marble in Jinping area by adopting the two-parameter nonlinear function fitting method. The results show that for the medium and hard rock, the expansion behavior strongly depends on the confining pressure and the plastic parameters of rock in the process of failure, and shows the non-linear evolution law which increases gradually with the increase of plastic deformation. The proposed two-parameter nonlinear dilatancy angle model describes well the volumetric expansion characteristics of the rock failure process. The results are useful to study the dilatancy mechanism of surrounding rock induced by the stress change of underground rock, the prediction of the volume expansion expansion zone and The reasonable design of surrounding rock support has certain theoretical and engineering application value.