考虑不同破坏形式下隧道锚承载力及破坏阶段研究

Study on Bearing Capacities and Failure Stages of Tunnel⁃Type Anchorage Considering Different Failure Modes

现有研究多以锚岩接触面出现塑性区域或应力峰值点转移作为达到极限状态的判别标准,但不同工程地质情况会导致隧道锚(TTA)破裂面线形存在较大差异,很难准确推导出隧道锚的极限承载力.为了进一步探求隧道锚在拉拔荷载下的工作过程,得到更加明确的隧道锚极限承载力的表达形式,采用幂指数函数形式表征倒锥形破坏破裂面的线形,基于Mindlin应力解与峰值剪应力控制理论得到界面破坏应力分布形式,推导了界面破坏与倒锥台破坏形式下的承载能力公式;采用国内5座悬索桥隧道锚承载力进行算例验证,同时分析研究了不同参数对隧道锚极限承载力的影响.研究表明:两种破坏形式下,承载力的主要来源为破裂面的黏结力,占总承载力的50%以上,承载力均随着长度与内聚力的增加而线性增加;承载力随着倾斜角的增加而增加,但增长速度减慢,界面破坏形式下出现先增加后减小的现象.对比以往试验以及数值模拟结果,与该文推导结果基本一致,分析公式计算结果和位移增长曲线,发现隧道锚工作过程明显呈现3个阶段,最终破坏形式为界面破坏和倒锥形破坏两种破坏模式的结合.

The existing studies mostly take the occurrence of plastic zones or stress peak point transfer on the contact surface of anchor rock as the criterion for the limit state.However,due to different engineering geolog-ical conditions,there are significant differences in the fracture surface alignments of tunnel anchors,and the ul-timate bearing capacity of the tunnel-type anchorage(TTA)cannot be accurately derived.To further explore the working process of the TTA under pull-out loading,the power exponential form was used to characterize the shape of the inverse cone damage rupture surface,based on Mindlin’s stress solution and the peak shear stress control theory.The interface failure stress distribution was obtained,the equations for the bearing capac-ities under 2 damage forms were given.Five domestic TTA suspension bridges were taken for example and veri-fication in both damage forms,and the effects of different parameters on the TTA load-bearing capacity were analyzed.The results show that,the main source for the bearing capacity is the cohesive force on the fracture surface,which is more than 50%of the total.The bearing capacity increases linearly with the length and the co-hesion force,and grows with the inclination angle at a slowing rate.The bearing capacity would first increase and then decrease with the inclination angle under the interface failure form.These derived results are basically in agreement with those previous experimental and numerical results.The analysis of the proposed analytical displacement curves indicates that,the working process of the TTA has 3 visible stages,and the final failure mode is a combination of the interfacial failure and the inverse cone failure.