滨海土岩地层浅埋暗挖车站临时支撑拆除优化分析

Optimization Analysis of Temporary Support Demolitionof Shallow Excavation Station in Coastal Soil and Rock Stratum

以滨海地区某地铁暗挖车站初支拱盖法开挖为例,采用有限元数值模拟方法对临时支撑拆除方案进行分析,并结合实测数据进行验证。结果表明:围岩沉降最大值位于拱顶部位,两侧拱腰附近的位移量小于拱顶,围岩表现出明显的收敛性;最后拆除与拱顶连接的竖撑对控制拱顶初支沉降效果较好,且在拆除过程中可保证横撑与竖撑有连接部分;优化后的拆除方案考虑二衬施作,下部竖撑采用间隔拆除的方法,拱脚二衬对拱盖上部围岩提供支撑保护作用,可控制拱顶附近发生过大沉降;拆撑时应加强监测,现场实测数据可见采用优化后的拆除方案,地表沉降、拱顶沉降与净空收敛变化趋势较为稳定。

An example was taken from the initial arch cover excavation of a subway station in the coastal area,the finite element numerical simulation method was used to analyze the temporary support demolition scheme that is subsequently verified by the measured data.The result shows that,the maximum settlement of surrounding rock is located at the vault,and the displacement near the arch waist on both sides is smaller than that of the vault,therefore,the surrounding rock has a noticeable convergence.Then,the vertical support connected with the vault is removed,which has a good effect on controlling the settlement of the initial support of the vault,and the connection between the horizontal support and the vertical support can be guaranteed during the demolition process;the optimized demolition scheme considers the construction of the secondary lining,and the lower vertical support adopts the method of interval demolition.At the same time,the secondary lining of the arch foot provides support and protection for the upper surrounding rock of the arch cover,which can control the excessive settlement near the vault.Finally,the monitoring measurement should be strengthened when the support is removed.The field measured data show that,the trend of surface settlement,vault settlement and clearance convergence is relatively stable after the optimized demolition scheme is adopted.