盾构近距离下穿既有车站沉降分析及控制措施研究

Settlement Analysis and Control Measures for a Shielded Tunnel Closely Crossing an Existing Metro Station

针对盾构机近距离下穿既有车站问题,以南京地铁7号线高庙路站至永初路站盾构区间下穿既有宁和城际永初路站为研究对象,采用MIDAS GTS NX有限元软件对施工过程进行数值模拟,基于现场实际监测,分析盾构下穿施工对既有车站沉降变形的影响。结果表明:盾构机在高富水粉细砂地层中掘进时,由于对周围地层扰动等原因,土体应力状态改变引起既有结构沉降变形;通过选择合理范围的地层加固、合理土压力值的设定以及减少停机时间等措施,同时控制好盾尾同步注浆、衬砌与地层间隙注浆填充,可以有效控制盾构施工引起的既有结构变形和地表沉降。

This paper presents a case history of a shielded tunnel of Nanjing Metro Line 7 from Gaomiao Road Station to Yongchu Road Station crossing the existing transit station.The MIDAS GTS NX finite element software is used to perform the numerical simulation on the entire construction process.Based on the actual monitoring data during the construction,the influence of the shielded tunnel construction on the settlement and deformation of the existing station is analyzed.The results show that when the shielded machine is excavating in the water-rich silty sand stratum,due to the disturbance to the surrounding soils,the change of the soil stress state causes the settlement and deformation of the existing structure;The existing structure deformation and the ground surface settlement caused by the shielded construction can be effectively controlled by selecting the reasonable range of the ground reinforcement,defining the reasonable earth pressure value,reducing the downtime and other measures,and at the same time controlling the grouting effects such as shielded tail synchronous grouting,lining and ground gap grouting filling.