软土盾构不同穿越形式对既有隧道扰动影响分析

Analysis of Disturbance Influence of Different Shield Crossing Forms of Soft Soil on Existing Tunnel

以上海某实际隧道叠交段土层分布为背景,采用3维有限元方法对新建隧道分别以先下后上夹穿、下穿和上穿3种形式穿越既有隧道施工过程进行模拟,分析了在每种穿越形式下既有隧道的变形,给出了每种穿越形式下控制既有隧道变形的合理措施.研究结果表明,在盾构开挖过程中,既有隧道圆形断面不仅出现变形,而且也出现了扭转;新建隧道先下后上夹穿既有隧道的控制重点不是既有隧道最终沉降,而是开挖过程中出现的最大沉降值;下穿形式下,控制重点为既有隧道最终状态沉降曲线;上穿形式下,控制重点为既有隧道的大幅度上浮.同时对比了实测和模拟数据,验证了数值模拟的可靠性.研究成果为地铁叠交段穿越形式的选择、施工及既有隧道保护技术提供了一定理论基础.

Based on an actual soil layer of tunnel overlapping section of Shanghai Metro, a 3-D finite element method is used to simulate the excavation process of three crossing forms of new tunnels, including crossing from upper and under of an existing tunnel, under crossing from an existing tunnel, and upper crossing from an existing tunnel. Settlement of the existing tunnel of each crossing form is analyzed. A reasonable measure is given to control settlement of the existing tunnel in each crossing form. The results show that there is not only deformation but also torsion of circular section of the existing tunnel. The key of a new tunnel crossing an existing tunnel from upper and under is to control the maximum settlement during the excavation process instead of final status settlement value of the existing tunnel. The key of a new tunnel under crossing an existing tunnel is to control the final status settlement curve of the existing tunnel. The key of a new tunnel upper crossing an existing tunnel is to control the floating upwards of the existing tunnel. Reliability of the numerical simulation is verified by comparison between the measured and simulated data. The results of this research provide a basis for choosing the form for a new tunnel crossing an existing tunnel, constructing new tunnels, and orotecting existing tunnels.