盾构法隧道施工引起的土体变形预测

 理论分析表明，不同土质条件下盾构法隧道施工引起的土体移动模型有区别。基于盾构法隧道统一土体移动模型，假定土体不排水，采用N. Loganathan等提出的研究方法，通过对Verriujt计算公式进行修正，推导得到盾构施工过程中由于土体损失引起的土体变形二维解，该方法适用于施工阶段。算例分析表明：所给出方法的计算结果与实测值较吻合，适用于从流塑～坚硬状态的所有黏性土。Loganathan公式只适用于流塑状态的黏性土，当土质较硬时，计算所得到的土体沉降要比实测值小；盾构施工引起的隧道上方土体沉降从地面向下呈非线性增大，在隧道顶部达到最大，离隧道越近，增长越快；隧道周围土体产生向隧道侧的水平位移，从地面向下逐渐增大，在略高于隧道轴线附近达到最大值，再逐渐减小直到0。离隧道越近，土体水平位移越大。

PREDICTION OF GROUND DEFORMATION INDUCED BY SHIELD TUNNELING CONSTRUCTION

Theoretical analysis shows that ground movement patterns induced by shield tunneling construction for different kinds of soils will be different. Assuming soil is undrained，the Verriujt¢s formula is modified by N. Loganathan¢s method. Based on uniform ground movement pattern of shield tunnel，two-dimensional analytical solution of soil deformation induced by shield tunneling construction is deduced；and the method is applied to different construction phases. As shown in analytical calculation，the predicted ground displacements are in good agreement with the measured values；and this method is applicable for the clayey soil from flow-plastic state to stiffness state. While Loganathan¢s formula is only fitted for flow-plastic state clay，the predicted ground settlements for stiffness state clay are smaller than the measured values. The settlement of soil above tunnel by shield construction increases nonlinearly from ground surface down to deep；and it reaches the maximum value in the roof of tunnel；the closer the soil to tunnel is，the faster the settlement is. The horizontal displacement of the tunnel surrounding soil increases from ground surface down to deep；but it reaches the maximum value over the tunnel axial line and then gradually reduces to zero. The nearer the soil to tunnel is，the larger the horizontal displacement of soil is.