花岗岩峰后力学特性试验与模型研究

Physical and numerical model tests on post-peak mechanical properties of granite

深部围岩在开挖卸载过程中表现出的峰后复杂力学特性一直是工程界十分关注的问题,深入研究岩石峰后力学行为对深部资源开采工程具有重要意义。以深部立井马头门工程为依托,通过室内试验方法研究花岗岩峰后力学特性,采用非线性拟合方法获得花岗岩峰后软化模量与围压的指数关系式,假定岩石的剪胀角为恒定值,基于塑性理论构建考虑围压及剪胀角影响的岩石峰后应变软化模型;以FLAC3D为平台开发数学模型并进行验证,通过构建马头门巷道数值模型,分析深部围岩在应变软化条件下的破坏特征规律。通过研究可知,花岗岩峰后破坏具有脆–延性转化趋势,在高围压条件下,岩石峰后表现出塑性软化破坏特征,岩石峰后软化模量随着围压的增大而减小;通过FLAC3D进行数值验证可知,构建的应变软化模型与试验数据基本吻合,所建立的应变软化模型具有较高的可靠性;通过数值模拟方法分析深部马头门巷道围岩破坏特征可知,巷道拱顶及拱脚等局部区域出现了塑性剪切应变,与现场巷道围岩破损位置及深度基本相同。

The deep surrounding rock in the process of excavation exhibits complex post-peak mechanical properties. It has long been an issue of great concern to the engineering. Thorough studies on the post-peak mechanical properties are of great significance to resource extraction projects. Based on the deep shaft horsehead project, the mechanical post-peak properties of the granite are studied by using laboratory tests. The nonlinear fitting method is used to obtain the exponential relationship between the post-peak softening modulus and confining pressure of granite. The rock dilatancy angle is assumed to be constant.A post-peak strain softening model is established considering confining pressure and dilatancy angle based on the theory of plasticity. Using FLAC3 D as the platform to develop and validate a mathematical model for horsehead tunnel to analyze the failure rules of the deep surrounding rock under strain softening conditions. The research results show that the post-peak destruction of granite has a trend of brittle to ductile transformation. Under high confining pressure, it exhibits plastic softening damage characteristic. The post-peak softening modulus increases with the decrease of the confining pressure. The FLAC3 D numerical verification shows that the results of the strain softening model agree with the experimental data, and that the proposed model is reliable. By analyzing the properties of horsehead roadway damage through numerical simulation, it is found that the plastic shear strain appeares in partial areas, such as the vault and arch foot, and that the location and depth are similar to the field ones.