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采用隐式锚索单元模拟地下洞室预应力锚索,探讨了索体对岩体单元的等效附加刚度贡献。针对预应力锚索的受力过程,分别分析了预拉力和围岩变形作用下锚索锚固段的受力机制。基于两种作用下锚固段内力的叠加,提出了一种考虑锚固界面剪切滑移的预应力锚索受力分析方法。结合三维非线性有限元,给出了预应力锚索受力的一般求解步骤,然后将此锚索算法应用于乌东德水电站左岸地下厂房洞室群分期开挖。结果表明,锚索支护能够有效加固岩体,限制破坏区的发展;锚固段轴力和剪应力均在始端达到最大,沿深度方向逐渐衰减。计算得到的锚固力变化过程与实测值基本吻合,验证了该算法的合理性。
The implicit anchor element is used to simulate the prestressed anchor cable in underground cavern and the equivalent additional stiffness contribution of cable body to rock mass is discussed. According to the stress process of prestressed anchor cable, the force mechanism of anchor cable anchorage section under pre-tension and surrounding rock deformation is analyzed respectively. Based on the superposition of the internal forces of anchorage section under two kinds of actions, a stress analysis method of prestressed cable considering the shear slip of the anchorage interface is proposed. Combined with the three-dimensional nonlinear finite element method, the general solution procedure of prestressed anchor cable stress is given. Then the anchor cable algorithm is applied to the staged excavation of the cavern group at the left bank of Wudongde hydropower station. The results show that the anchor cable support can effectively reinforce the rock mass and restrict the development of the damaged area. The axial force and shear stress reach the maximum at the beginning and gradually decrease along the depth. The calculated change of anchoring force is in good agreement with the measured value, which verifies the rationality of the algorithm.