交叠隧道盾构法施工土体变形的三维数值模拟

以正在建设中的上海市轨道交通明珠线二期工程上、下行线近距离交叠区间隧道盾构施工为研究对象，按“先下后上”的盾构推进过程，采用三维弹塑性有限元法SNSYS程序软件模拟了交叠隧道土层位移以及地表沉降曲面在盾构推进中的发展变化，得出了地面最大沉降量在上行隧道推进后将出现大幅度增长，且在推进前期沉降增幅最为显著的结论。给出了隧道周围土体塑性区的大小与分布，论证了要将地面沉降控制在允许范围内，必须在上、下行隧道施工中进行预注浆加固，以重点控制盾构推进前期的地层沉降量。最后，探讨了盾构刀盘推进力、一次推进步长、隧道埋深及地表硬壳层等多种影响因素对地面沉降的贡献。

3-D Numerical Simulation of Ground Surface Settlement under Overlapped Shield Tunneling

Based on the suggested driving process of overlapped shield tunnel,a true thsee dimensional elasto plastic finite element analysis is taken into account in this paper.Results show that after the lower tunnel is first driven through,ground settlement and horizontal displacement in soil strata will produce a significant increment in the earlier period of excavating the upper tunnel and its value is approximately up to four times as much as before.So it is essential to take strengthening measure by grouting for nearly saturated and severely disturbed soft soil around the tunnel.Soil plastic zone is given for different sections along the designated route line.Some influence factors effected on ground settlement during the overlapped shield driving are also evaluated.