端部锚固锚杆预应力场分布特征的大型模型试验研究

 为了研究预应力端部锚固锚杆预应力场在围岩体中的分布特征，设计并制作大型锚杆支护应力场测试试验台。试验结果表明：(1) 单根锚杆的应力场在空间中的分布形态类似于“石榴”状，随着扩散半径的增大应力等值面的分布逐渐由密到疏，应力值逐渐由高到低，分布范围逐渐由小到大；(2) 在锚杆自由段两端和锚固段附近分别形成了2个压应力相对集中区和1个拉应力相对集中区，压应力主要分布在锚杆自由段附近围岩内，并向锚固段附近围岩扩散；(3) 应力沿着锚杆轴线方向的分布规律与测线和锚杆之间的距离有关，应力沿着水平方向的变化规律与测线和模型表面之间的距离有关；(4) 预紧力不同，应力场的宏观分布形态基本一致，但同一应力等值面的分布范围将发生显著改变。试验结果对更深入认识锚杆支护作用机制和工程中优化锚杆支护设计方案均有一定的指导意义。

Large scale model test on the distribution characteristics of the prestressed field of end-anchored bolts

A large scale field test bench for prestressed bolt was manufactured to study the distribution characteristics of the prestressed field around the end-anchored bolt. The results show that the distribution pattern of the prestressed field of a single anchor is similar to the shape of pomegranate. The stress contour surfaces vary gradually from dense to sparse，the stress values descend gradually and the distribution ranges enlarge gradually. Two concentration zones of compressive stresses form in the rock in the vicinity of the anchorage and a concentration zone of tensile stress forms near the anchor head. The distribution of the stress along the axis of the bolt is related to the distance between the measuring line and the anchor bolt. The variation of the stress along the horizontal direction is related to the distance between the measuring line and the surface of the model. Although the pre-loads are different，the stress field distributions are basically the same，but the distribution ranges of the stress contour surfaces change significantly.