暗挖隧道下穿既有地铁线路加固措施研究

Study on Reinforcement Measures for an Excavated Tunnel Underpassing an Existing Subway Line

新建隧道近距离下穿既有地铁线路,易导致既有地铁线路发生较大沉降,影响列车行车安全。为确保施工安全性,减少对既有地铁线路的影响,分别建立三种加固方案的有限元模型,对比分析不同辅助加固方案控制既有线沉降的效果。结果表明:(1)加固新建隧道与既有线之间的夹层土可有效控制变形,尤其适用于砂卵石地层,可通过注浆填充空隙,提高土体密实度和强度,控制土体沉降。(2)注浆隔断方案对控制暗挖隧道拱顶沉降和净空收敛效果不佳,隧道与车站连接处差异沉降超过安全标准;注浆+管棚联合加固方案优于单一管棚加固。经过对比选用注浆+管棚联合加固方案以更好保证隧道施工过程的安全。

The construction of a new tunnel in close proximity beneath an existing subway line is prone to inducing significant settlement in the latter,potentially jeopardizing train operation safety.To ensure construction safety and minimize the impact on the existing subway line,this study establishes finite element models for three reinforcement schemes,comparing the effectiveness of different auxiliary reinforcement methods in controlling settlement of the existing line.The results indicate that:①Reinforcing the interlayer soil between the new tunnel and the existing line effectively controls deformation,particularly in sandy pebble strata.This is achieved by grouting to fill voids,enhancing soil density and strength,and reducing soil settlement.②The grouting cutoff method proves ineffective in controlling vault settlement and clearance convergence in the tunnel,with differential settlement at the tunnel-station interface exceeding safety standards.The combined reinforcement approach of grouting and pipe roof outperforms single pipe roof reinforcement.Based on the comparison,the combined reinforcement scheme of grouting and pipe roof was selected to ensure safety during tunnel construction.