大断面盾构隧道施工抗浮计算研究

Analysis on Anti-Buoyancy Caculation In Excavation of Big Cross-Section Shield Tunnel

基于大断面盾构隧道施工中经常碰到的上浮问题,首先讨论了盾构隧道施工中管片上浮的原因:水、注浆所用浆液、泥水盾构所用泥浆等所产生的浮力,以及建筑间隙的存在、施工过程对上覆土的扰动等,都可能是盾构管片上浮的原因。进而对盾构隧道抗浮问题进行了计算分析,在上覆土荷载及管片自重荷载之和小于管片所受浮力的情况下,重点考虑了邻接管片对上浮管片的约束作用(管片环间的摩阻力以及管片纵向连接螺栓自身的抗剪切能力),以及剩余力对上覆土产生的压缩效应。分析结果表明:隧道上浮问题的产生与否不仅与管片自重、上覆土荷载以及受到的浮力大小有关,也与管片本身特性有关;隧道抗浮控制既可以从改善上覆土性能,增加上覆土厚度入手,也可以从改善管片自身受力性能入手,诸如增加纵向螺栓数量、加大螺栓直径、加大螺栓紧固力、设置剪力键等。

Segments floating is a main problem often met in shield tunnel excavation. The reasons of shield tunnel segments floating are discussed first, including the buoyancy produced by water, grouts or slurry, the gap produced by shield shell, and the disturbance produced by excavation to overburden soil, etc. Then, the problem of resisting the segments floating of shield tunnel is analyzed. In the analyzing process, both the restriction force of neighboring segments on the floating segments （ including the friction between segment rings and the shearing resistance of longitudinal bolts ） and the compression effect of Remain - Force on overburden soil are taken into account, in the case that the general weight of overburden and segments self- weight is smaller than the buoyancy. The analysis resuit indicates that the problem of shield segments floating is concerned with the self- weight of segments, overburden , the buoyancy, and the characteristics of the segments. To control the segments floating of shield tunnel, the methods not only include improving the quality of covering soil, increasing the thickness of covering soil, but also include improving the mechanical characteristics of the segments, such as adding the number of longitudinal bolts, enlarging their diameters, increasing their fastening force, and setting shearing force bond, etc.