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地下和边坡工程开挖常涉及岩体卸荷问题,采用ABAQUS软件中的扩展有限单元法(extended finite element method,XFEM)对开挖卸荷过程岩体内部裂纹的起裂扩展进行了模拟,通过计算裂纹尖端应力强度因子研究了其起裂特征,并探讨了起裂影响因素,通过记录裂纹扩展形态研究了其动态演化模式.结果表明,卸荷过程中卸荷速率越快,裂纹长度越长,倾角越大,其起裂越容易;并且裂纹面受到的正应力不断减小,剪应力不断增大,裂纹扩展主要由剪应力控制,这与理论分析结果一致.裂纹最终扩展演化形态也与物理试验相近,充分表明运用扩展有限单元法研究岩体裂纹问题的可靠性.
The excavation of underground and slope engineering often involves the unloading of rock mass. The extended finite element method (ABAQUS) is used to simulate the crack initiation and propagation in the rock mass during excavation and unloading. The crack initiation characteristics were studied by calculating the stress intensity factor at crack tip, and the influencing factors of cracking were discussed. The dynamic evolution mode of crack initiation was studied. The results show that the faster the unloading rate is, the longer the crack length The bigger the angle is, the easier it is to crack. And the normal stress on the crack surface decreases, the shear stress increases, and the crack propagation is mainly controlled by the shear stress, which is consistent with the theoretical analysis. Similar to the physical experiment, it shows the reliability of using extended finite element method to study the rock mass crack problem.