砂卵石地层地铁近接下穿既有盾构区间施工控制技术

Construction Control Technology of Metro Passing through the Existing Shield under the Sand Pebble Stratum

为探究地铁暗挖近接施工下穿既有盾构区间加固技术适应性,以成都5号线近接下穿既有3号线为工程背景,提出适应于成都砂卵石地层的预埋注浆加固保护方案,且通过数值模拟研究了不同注浆加固范围的保护效果、注浆过程对隧道结构影响以及对下穿过程规律性进行讨论,并结合现场监测分析。结果表明:既有隧道注浆加固范围扩大,其隧道结构变形呈线性减小,隧道结构纵向沉降槽呈线性缩小,适当增大既有隧道注浆范围可控制其变形量;预埋钢花管注浆加固过程中,浆液压力和土体硬化将导致既有隧道结构竖向产生沉降,水平方向相向靠拢;地铁下穿过程中,既有隧道结构主要产生竖向沉降,先缓慢沉降,隧道穿过后沉降变形突增,再趋于稳定,前期有一定反应阶段;相比既有隧道,近距离的大范围注浆加固导致土体硬化,5号线结构变形预变形阶段极大缩短,反应时间短,施工风险增大。提出二次衬砌工序优化、深孔注浆加固补救措施以及节点位置格栅密排等措施能够降低既有盾构运营风险。

In order to explore the adaptability of the reinforcement technology of underground excavation and passing through the existing shield tunnel,Chengdu line 5 passing through the existing line 3 was taken as the engineering background.The embedded grouting reinforcement protection scheme suitable for Chengdu sandy pebble stratum was put forward,and the protection effect of different grouting reinforcement range,the influence of grouting process on the tunnel structure and the regularity of the underpass process were studied through numerical simulation.The main conclusions are as follows:the scope of grouting reinforcement of the existing tunnel is expanded,the deformation of the tunnel structure is linearly reduced,the longitudinal settlement groove of the tunnel structure is linearly reduced,and the deformation can be controlled by properly increasing the grouting scope of the existing tunnel;in the process of grouting reinforcement of embedded steel tube,the grouting pressure and soil hardening lead to the formation of the existing tunnel;in the process of subway underpass,the existing tunnel structure mainly produces vertical settlement.The settlement develops slowly at first,the settlement deformation increases abruptly after passing through the tunnel and then tends to be stable.There is a certain reaction stage in the early stage;compared with the existing tunnel,due to soil hardening caused by large range grouting reinforcement within short distance,the structural deformation of line 5 changes in advance,the shape stage is greatly shortened,then response time is short and construction risk is increased.Based on the analysis,aiming at the construction risk of line 3,it is proposed that the optimization of the secondary lining process,the remedial measures of deep hole grouting reinforcement and the measures of grid dense arrangement at the node position can reduce the risk of operating existing excavation.