隧道锚抗拔承载力及安全性评估方法

Uplift Bearing Capacity and Safety Assessment Method of Tunnel-type Anchorage

针对当前隧道锚承载力估值时未考虑锚-岩联合承载,安全性评估中忽略传力构件可靠性的问题,基于楔形效应和隧道锚承载的阶段性特征,推导隧道锚的极限承载力估值公式。综合考虑锚碇系统中传力构件的承载能力和隧道锚的抗拔力,反推得到系统所能承受的拉拔荷载上限值,进而对整个隧道锚系统中各部分的安全性进行评价,且以伍家岗大桥北岸隧道锚工程为依托验证方法的合理性。分析发现:伍家岗大桥隧道锚考虑楔形效应的极限承载力为3 080MN,是规范计算方法的7倍;传力构件的安全性限制了系统所能承受的拉拔荷载上限值,最大拉拔荷载为486 MN;地质力学模型试验揭露的隧道锚初始抗力为9倍设计缆力,极限承载力为13倍设计缆力,建议公式所对应的结果分别为7倍和14倍。结果表明:隧道锚的楔形效应极大地提高了锚-岩联合体的极限承载力;锚碇系统的安全性应由锚-岩联合承载性能和传力构件可靠性两方面综合确定,承载能力低者为系统承载能力的控制性因素;只有从综合角度对锚碇系统的安全性进行评估,才能确保系统安全可靠;建议的承载力估值公式与试验结果吻合性较好。

Many problems still remain in the reliability analysis of the bearing capacity of tunneltype anchorages.For example,the action of rock and anchor shared load together is neglected in the design of the tunnel-type anchorages.Moreover,the reliabilities of transmission components are not considered in the safety assessments of anchorages.First,to compensate for the insufficiency mentioned above,the formula for the ultimate bearing capacity of the anchorage was deduced,taking into consideration the wedged effect and the bearing characteristics.Besides,the maximum load that the anchor rock system could bear was evaluated by comprehensive considerations of the capacities of the transmission components and the anchor rock system.With the resulting value,the safety of each part of the anchorage system was analyzed.Moreover,the assessment method was validated by an engineering example.Through the verification,it can be seen that the ultimate bearing capacity,taking into consideration the wedged effect,can reach3 080 MN.This value is seven times larger than the value obtained from the assessment that neglects the wedged effect.Furthermore,the maximum load that the anchor rock system can bear is only 486 MN,because of the capacities of the load arms.The original resistance and the maximum bearing capacity of the anchorage,revealed by three-dimensional（3 D）geological modeling tests,are 9 and 13 times larger than the design load,respectively,while,using the recommended formulas,these values are calculated as 7 and 14 times respectively.From the results above,the following can be concluded：the wedged effect improves the ultimate bearing capacity of the anchor rock system tremendously,and the security of the anchorage system should be evaluated by comprehensive considerations of the capacities of the load arms and the anchorrock system.The weaker of the two（the load arms and the anchor-rock system）controls the bearing capacity of the anchorage system.The security of the entire anchorage system can therefore be guaranteed by comprehensively assessing the system safety.Finally,the recommend valuation formula for the anchorage bearing capacity is in good agreement with the results of the laboratory modeling test.