盾构法隧道统一土体移动模型的建立

首次提出土质软硬决定了盾构隧道周围土体的移动方向,移动焦点在隧道中心点与隧道底部位置之间变动。采用两圆相切的土体损失模型,通过引入移动焦点的坐标参数,建立了统一的土体移动模型,该模型能将Park模型与Loganathan模型包括在内。假定土体不排水,利用源汇法推导了由土体损失引起的盾构隧道轴线上方地面最大沉降量Smax的通用计算公式和上、下限解。理论分析表明:无论土质如何变化,土体损失引起的Smax值总在上、下限解范围内。理论解与27例工程实测值和Peck解进行了比较,结果表明:21例实测值在上、下限解范围内,6例实测值超出该范围,但与上、下限解非常接近,超出量小于10%;Peck公式计算得到的Smax值也都在上、下限解范围内,仅有1例略微偏大,从而验证了本文方法的正确性。本文方法也适用于顶管法施工。

Establishment of uniform ground movement model for shield tunnels

Ground movement pattern of shield tunnels was investigated.It was firstly put forward that the direction of ground movement was conditioned by soil types,and the novel parameter “movement focus” moved between the center and bottom of tunnel.Ground loss model of two tangent circles was adopted to establish a uniform ground movement model for shield tunnels by introducing the coordinate parameter of movement focus.This novel model included Park pattern and Loganathan pattern.Smax was the maximum surface settlement above the tunnel centerline induced by ground loss.Assuming that soil was undrained,the general calculation formulas for Smax,upper limit bounds and low limit bounds were deduced by use of the virtual image method.It was shown by theoretical analysis that Smax was always in the range of upper and lower limit bounds no matter what the soil type was.By comparing theoretical values with measured values from twenty-seven actual tunnels and with Peck values respectively,it was shown that:(1) twenty-one actual values were in the range of upper and lower limit bounds,six actual values were beyond but close to the bounds,with difference generally within 10%;(2) values of Smax calculated by Peck formula were also in the range of upper and lower limit bounds,while only one value was a bit larger.The above comparison evaluated the validity of the present calculation method.It would be applicable in pipe-jacking construction.