金沙江大桥隧道式锚碇的安全评价

Safety evaluation on tunnel-type anchor blocks of Jinsha River bridge

以华丽高速公路金安金沙江大桥华坪岸和丽江岸隧道式锚碇的安全评价为依托,利用工程类比法评价其稳定控制要素,设计了数值超载试验。试验结果表明:根据塑性区的扩展过程,确定隧道式锚碇围岩的破坏模式,明确施工安全监测和需要采取预加固部位的空间位置。根据荷载与位移关系曲线的拐点和塑性区贯通判据,确定华坪岸锚碇和围岩系统设计承载力大于6.5P,丽江岸锚碇和围岩系统设计承载力大于5.0P;认定锚碇和围岩系统承载稳定系数均大于4.0。在该设计荷载的作用下,围岩承载安全。根据有限元计算结果的数值积分,考虑规范规定的Ⅰ-Ⅰ和Ⅱ-Ⅱ最不利截面的评价结果,华坪岸隧道式锚碇的抗拔稳定系数取6.2,丽江岸隧道式锚碇的抗拔稳定系数取2.6,均满足抗拔稳定系数大于2.0的规定。该研究成果可为设计验证和工程实践提供参考。

The tunnel anchor blocks’stability of Huaping and Lijiang sides is studied.Using engineering analog method estimates its key influencing factors of the stability.The overload numerical simulation is designed.Main conclusions are drawn by the analysis of numerical tests as following:the propagation of plastic zone presents a fail mode of tunnel anchor block&rock mass,and indicates that key parts for monitoring&pre-reinforcement exist.According to P-S curve’s spinodal and plastic zone cut-through,the designed bearing capacity of anchorage-rock system of Huaping side is greater than6.5times of the initial design cable force,that of Lijiang side is greater than5.0times of the initial one,surrounding rock stable safety factors based on them are all larger than4.0,which can meet the requirements of specification and proves that the initial design cable force is safe.On basis of integration of FEM computing results and evaluation results ofⅠ-ⅠorⅡ-Ⅱsections specified by standards compared with each other,the minimum of uplift safety factor of Huaping side’s tunnel anchorage is6.2,that of Lijiang one is 2.6,which can all meet the requirements of uplift safety factor larger than2.0.All of these can be used in the design and the engineering practice.