卵石地层中地铁盾构近距下穿盾构隧道施工沉降控制

On Settlement Control of Shield Tunnels Underneath Traversing Existing Dual Shield Tunnels in Gravel Layer

为研究卵石地层条件下盾构下穿施工时既有盾构隧道的沉降特征及其控制措施,依托北京地铁16号线盾构下穿既有地铁4号线盾构隧道工程,通过分析既有隧道沉降的数值模拟结果,结合现场监测数据和盾构施工参数,探讨了盾构的适应性改造,总结了隧道沉降的规律,阐明了调控盾构施工参数的经验。研究表明,为适应卵石地层条件,盾构须提高构件耐磨性、增设注浆及泡沫系统;既有隧道沉降在盾构通过时变化较大,而在盾构到达前和通过后变化较小,且盾构施工的再次扰动影响显著;为有效地控制既有隧道沉降,盾构施工参数应根据监测数据实时调控,保持较高的土仓压力和顶推力,通过提高注浆压力确保注浆质量。

In order to study the settlement regulation and control measures of shield tunnels underneath traversing existing dual shield tunnels in gravel layer,the precedent project that dual shield tunnels of Subway Line 16 traversed shield tunnels of Subway Line 4 in Beijing was taken as an example.By analyzing the numerical simulation and in-situ monitoring data of settlement,the settlement variation trends of existing tunnels caused by traversing construction were clarified.Meanwhile,adaptive transformation of the shield machine was discussed.And the experience of shield construction parameters control was summarized.Research shows that:1)The shield machine must improve its abrasion resistance,and add grouting system and foaming system in order to accommodate the gravel layer.2)The settlement of existing tunnels is relatively large in the range when shield machine is traversing.However,it is small before shield machine arrives and after shield machine traverses.Meanwhile,the settlement of existing tunnels is obviously affected by the secondary disturbance of successive construction.3)In order to restrain the settlement of existing tunnels effectively,the shield construction parameters must be controlled in real time according to monitoring data and parameters of thrust force and working chamber pressure must be kept high relatively.Meanwhile,quality of grouting must be ensured by enhancing grouting pressure.