锚杆拉拔过程中锚固体系传力规律研究

Study on force transfer mechanism on anchorage system in the process of bolt drawing

开展锚杆拉拔过程中锚固体系传力规律的实验研究。通过设计锚杆拉拔实验模型,并以应变片和数字散斑相关方法作为实验测试手段,分析锚杆拉拔过程中锚杆传力、锚固体系变形场演化、锚固剂与围岩界面变形演化、锚固剂与围岩位移及锚固剂与围岩相对位移演化特征。研究结果表明:1)锚杆竖向应变随与锚固端部距离增加而减小,相邻两测点轴力差值演化特征与锚杆锚固剂界面的摩擦类型相关;2)锚固体系变形场演化特征为:在锚杆拉拔过程中,锚固体系变形主要集中于锚固剂与围岩界面处,随着拉拔力增加变形集中区域从锚固端部沿锚固方向向深部扩展;3)锚固剂与围岩界面变形演化特征为:初始拉拔阶段,界面变形沿锚固方向呈单调递减趋势,随拉拔力增加,界面变形沿锚固方向呈先增后减趋势,且变形最大值固定于近锚固端部的某一锚固深度;4)锚固剂与围岩位移演化具有一致性特征,总体经历了弹性变形阶段、塑性变形及扩展阶段、变形回弹阶段,锚固剂与围岩的相对位移演化速率与锚固剂和围岩的变形阶段相关。

By independently designing experimental model, the experiments of bolt pullout were carried out to study the rule of mechanics transfer on anchorage system. The digital speckle correlation method and the strain measurement were used to measure the deformation of experimental model in the process of bolt drawing. The characteristics of the bolt force transfer, deformation field evolution on anchorage system, the interface deformation evolution between anchorage agent and surrounding rock were analyzed. The evolution characteristics of anchorage agent displacement, surrounding rock displacement, and the relative displacement of both were studied. The results show that: The vertical strain of bolt decreased with increasing distance from anchor end. The evolution characteristics of axial force different value between two adjacent points corresponded to the friction type of the interface between bolt and anchorage agent. The deformation of anchorage system was mainly concentrated on the interface between anchorage agent and surrounding rock. The deformation concentrated area of anchorage system extended from the anchor end to the deep part along the anchorage direction with the drawingforce increased. The interface deformation evolution trend between anchorage agent and surrounding rock was monotonically decreased along the anchorage direction during initial drawing stage. With the drawing force increased, it increased firstly and then decreased along the anchorage direction, and the maximum deformation value was fixed at the location of some anchorage depth near anchorage end. The displacement evolution characteristics of anchor agent and the surrounding rock were the same. The anchor agent and the surrounding rock went through elastic deformation stage, plastic deformation and propagation stage, deformation springback stage. The relative displacement evolution rate of both was related to displacement evolution stage of them.