不同围压下煤岩变形与剪胀扩容模型

Deformation characteristics and dilatancy model of coal rock under different confining pressures

在RMT-150B岩石力学试验系统上进行了煤岩的变形和剪胀特性研究,获得如下结论:随着围压增加煤岩均质性明显提高,峰值前变形特性基本趋于一致,屈服阶段逐渐增长;煤岩体变扩容初始点发生在应变硬化阶段,最大扩容率在应变软化阶段,且随着围压增加体变对围压的敏感性减小;为了准确表达煤岩在破坏过程中的非线性体积变化行为,建立了同时考虑塑性剪切应变和围压影响的煤岩剪胀角模型,该模型表明在较小塑性剪切应变下剪胀角即达到峰值,之后不断缓慢回落,围压越小对应的剪胀角峰值越大,小围压下峰值剪胀角对应的塑性剪切应变也较小。

At present, it is usually assumed that the dilation angle is constant in analysis, this assumption can not accurately express the nonlinear volume change behavior of rock in the failure process. Thus based on the deformation characteristics of coal rock under different confining pressures, established the dilation angle model of coal rock considering plastic shear strain and confining pressures, the model shows that dilation angle reaches the peak value at a small plastic shear strain, then gradually falls. The smaller the confining pressures is, the bigger the dilation angle peak value will be. There are great differences between the actual dilation angle of coal rock in failure process and dilation angle set constant in analysis at present. The analysis of the experimental data of coal rock under confining pressures, shows that with the increasing of confining pressure, coal rock heterogeneity increases, deformation characteristic before peak value assimilates, and the yield stage gradually increases. The initial point of expansion at the strain hardening stage, while the maximum expansion rate occurred at the strain softening stage, and the volume strain sensitivity relative to confining pressure decreases with the increasing of confining pressure.