盾构施工引起的固结沉降分析

Analysis of consolidation settlements caused by shield tunneling

盾构在低渗透性土层中开挖,常常伴随着地表下沉,究其原因为超孔隙水压力消散引起固结沉降的结果。为对盾构施工引起土体的固结沉降进行研究,首先,根据隧道施工前后土体应力的变化值,应用Henkel超孔隙水压力理论,推导了隧道开挖引起的初始超孔隙水压力的计算公式,并采用数值分析方法,考虑了由于土体的固结引起的沉降变形。研究成果应用到上海地铁2号线,根据具体的地质条件进行理论计算分析。结果表明,隧道开挖引起的初始超孔隙水压力最大值位于隧道起拱线处,地表固结沉降预测值与实测值吻合较好。

Following a tunnel excavation in low-permeability soil, it is commonly observed that the ground surface continues to settle with time, as the dissipation of the excess pore pressure leads to the consolidation settlements. For studying the consolidation settlement of soil caused by shield tunneling, an initial excess pore water pressure formula during the tunnel construction is presented based on Henkel pore water pressure theory; and it can be used to calculate the consolidation settlement by means of numerical analysis. This approach has been applied to the engineering case of the Shanghai metro tunnel-line 2; and the calculation results are obtained based on the soil geological condition. As shown in the analytical calculation, the maximum value of the initial excess pore water pressure is located at the spring-line of the tunnel. The calculation results of the consolidation settlements are in good agreement with the field data.