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以大型地下洞室为背景,采用隐式锚杆柱单元模拟黏结式岩石锚杆,推导了杆体对围岩模型的附加刚度贡献模型。根据中性点理论,假定锚固体界面的剪切滑移模型,导出了锚杆与围岩相互作用下的荷载传递基本微分方程。基于三维弹塑性有限元增量法计算的围岩离散位移,采用插值拟合获得造成锚杆变形的围岩连续位移,通过求解微分方程得到锚固体界面剪应力和轴向力分布函数。将获得的锚固体剪应力采用等效附加应力模型作用于岩体,反映了锚杆的支护效应。实例分析表明,锚杆新算法能较好地模拟锚杆支护效果。获得的锚固体受力分布特征符合中性点理论,锚固体界面剪应力分为正、负两段,锚固体轴向力分布为单峰曲线。此外,新方法的计算值与实测值较为接近。
Taking the large underground caverns as the background, the imposing anchor bolt unit was used to simulate the cemented rock bolt, and the contribution model of the additional stiffness to the surrounding rock model was deduced. According to the neutral point theory, the shear slip model of the interface of the anchor is assumed, and the basic differential equation of load transfer under the interaction of rock bolt and surrounding rock is deduced. Based on the three-dimensional elasto-plastic finite element method, the displacement of surrounding rock was calculated. The displacement of surrounding rock which caused the rock bolt deformation was obtained by interpolation fitting. The interface shear stress and axial force distribution function were obtained by solving the differential equation. The obtained anchor shear stress acts on the rock mass with the equivalent additional stress model, which reflects the supporting effect of the anchor rod. The case study shows that the new bolt algorithm can simulate the effect of bolt support. The obtained stress distribution characteristics of anchors conform to the neutral point theory. The shear stress at the interface of anchors is divided into positive and negative segments, and the axial force distribution of anchors is a single-peak curve. In addition, the calculated value of the new method is closer to the measured value.