大型地下洞室全长黏结式岩石锚杆锚固机制研究及锚固效应分析

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。

Study of anchoring mechanism and analysis of anchoring effect of fully grouted rock anchor in large-scale underground caverns

In this study, the implicit cylindric anchor bar element is adopted to simulate the bonding rock bolt in the large underground caverns. Then an additional stiffness model of the anchor bolt attached to the surrounding rock is established. According to the neutral point theory, the differential equation of load transfer relating to the interaction between the surrounding rock and the bolt is deduced, by assuming the shear slip model on the interface of anchorage bolt body. Based on the discrete displacement of surrounding rock obtained by 3D elastoplastic finite element incremental method, the continuous displacement of surrounding rock which causes the deformation of bolt is acquired by using the interpolation and curve fitting. Furthermore, the distribution functions of the axial load and the shear stress on the interface between the bolt and surrounding rock are obtained by solving the differential equation. The shear stress is transformed into the equivalent additional stress acting on the rock mass, and thus the supporting effect of the bolts can be reflected. This case analysis shows that the new algorithm can be well used to simulate the supporting effect of bolts. It is also found that the anchorage stress distribution obeys the neutral point theory. As a result, the function of shear stress on the interface between the bolt and surrounding rock can be divided into positive part and negative part by the neutral point, and the axial load distribution of bolt is a unimodal curve. In addition, the calculated values by the new method show good agreement with the measured values.