盾构隧道与箱涵交叠下穿铁路稳定性控制措施研究

Research on stability control methods for shield tunnels overlapping box culverts under-crossing existing railways

为确保盾构隧道与箱涵掘进过程中围岩的稳定和铁路路基沉降与变形在允许范围之内,采取合适的开挖方案以及相应的加固措施至关重要。为此,依托厦门地铁6号线,借助有限差分软件FLAC3D和现场监测数据,对隧道和箱涵交叠下穿铁路不同施工工况下结构特征位置点、地表变形和铁路路基变形加固措施进行分析,得出以下结论:(1)通过对隧道和箱涵结构特征位置点与地表位移等进行深入研究,得出最优开挖方案为先箱涵开挖、后盾构右线开挖、再左线开挖;(2)围岩和路基在未加固的情况下,箱涵发生主动破坏时,变形发展至地面,加固之后,盾构隧道与箱涵开挖面附近破坏土体慢慢变为只发生在开挖面前方,而不会向上发展;(3)现场监测数据得出地表位移、隧道拱顶和箱涵顶部位移均有随时间逐渐增大的趋势,而隧道净空收敛无太大变化。隧道与箱涵开挖面支护应力监测值都在一个范围内波动,将其和数值结果对比可发现数值与现场实测结果较为吻合。

It is crucial to adopt appropriate excavation plans and corresponding reinforcement measures to ensure the stability of the wall rock and settlement deformations of railway roadbeds within an allowable range during shield tunnel and box culvert excavation projects.To this end,based on Xiamen metro line 6 and with the help of fi nite difference software FLAC3D as well as on-site monitoring data,the structure characteristic positions,ground and railway roadbed deformations and reinforcement measures of tunnels overlapping box culverts and underpassing existing railways under various construction conditions were analyzed.In doing so,the following conclusions were obtained:(1)By conducting in-depth research on the structure characteristic positions and surface displacement of tunnels and box culverts,the optimal excavation plan was determined.This plan involves box culvert excavation first,followed by shield driving on the right side of the support structure before tunneling on the left side.(2)When the surrounding rock and roadbed lack reinforcement and the box culvert experiences active failure,the deformation may extend to the ground level.After reinforcement,the damaged soil near the heading face of the shield tunnel and box culvert gradually transitions to occurring solely in front of the heading face and does not propagate upwards.(3)On-site monitoring data shows that ground displacement,tunnel arch top and box culvert top displacement all show a gradually increasing trend over time.Meanwhile,the convergence of tunnel clearance does not show any signifi cant changes,and the stress monitoring values of tunnel and box culvert heading face supporting forces fl uctuate within a certain range.Upon comparing these with the numerical results,it was found that the values align well with the on-site measured results.