浅埋大直径盾构隧道施工期衬砌上浮及地表隆起的模型研究

Modeling of Tunnel Lining Up-lifting and Ground Surface Heave during Excavation of Large Diameter Shield Tunnel under Shallow Overburden

为解决大直径盾构隧道施工过程中出现的浅覆土段隧道衬砌上浮与地表隆起问题,以上海虹梅南路越江隧道工程为背景,对该问题开展理论研究。将引起隧道上浮的上浮力作用分解为基于浆液时变性的静态上浮力和由注浆压力产生的动态上浮力;分别定义上浮力分布段及浆液凝固段的等效地层弹簧刚度系数,基于Winkler地基梁理论建立衬砌上浮模型;由衬砌上浮位移量计算开挖面上部土体的挤压宽度,土体经挤压隆起引起地层"反向损失",继而求解隧道轴线上方地表横断面隆起曲线及沿隧道长度方向地表位移曲线。结果表明:1)模型计算所得地表横断面的隆起曲线呈正态分布,与实测数据吻合较好;2)沿隧道长度方向地表位移计算值能够较准确地预测地表最大上浮位移,且在地表上浮位移隆起量减少前与实测数据吻合较好;3)地表隆起位移只在盾尾离开后一段时间内存在,其值先增大后减小,最终趋于0。

The problem of tunnel lining up-lifting and ground surface heave during the excavation of large diameter shield tunnel under shallow overburden has been theoretically investigated with the project of Shanghai South Hongmei Road river-crossing tunnel.The buoyancy which causes the tunnel lining up-lifting is classified into the time-dependent static buoyancy of slurry and the dynamic buoyancy generated by grouting.Equivalent formation spring stiffness coefficients are defined for the section where the buoyancy is available and the section where the slurry has hardened, respectively,after which the model of tunnel lining up-lifting is established according to the theory of Winkler foundation beam.The resulting lining displacement is used to calculate the squeezing width of the soil above the excavation surface, which is further converted into " reverse loss" of soil formation.And then the uplift curves for ground surface in transverse and longitudinal directions are derived.The results indicate that:(1) The predicted ground surface heave in transverse direction is characterized by normal distribution and matches well with the data measurement.(2) The model accurately predicts the maximum ground surface heave in longitudinal direction and matches well with the data measurement until the heave drops.(3) Furthermore,ground surface heave exists only within a certain period after the shield passes and its value firstly increases and then decreases to zero.