针对大断面矩形顶管隧道施工穿越混合地层所引起的地表沉降变形,利用有限差分软件分析了5种不同空间组合的上软下硬混合地层中大断面矩形顶管施工引起的地表沉降特征,并与现场实测结果进行了对比分析,论证了上软下硬地层组合中土层厚度对地表沉降变形的影响规律,引入修正的非线性模型量化软、硬土层厚度对沉降槽宽度系数的差异化影响。结果表明:(1)随混合地层中软土层占比增大,地表沉降值不断增大,地层变形主要发生在上部软土层,地表沉降槽呈“V”形向两侧扩展,符合高斯分布;(2)地表最大沉降量与软土层占比呈近似线性关系,沉降槽宽度系数与断面软土层占比呈现非线性关系,修正的非线性理论公式较好地表征了上软下硬地层组合中各土层对沉降槽宽度系数i的影响规律,上部软土层和下部硬土层的系数分别为0.475和0.95,0.26和1.1。

In response to the surface settlement deformation caused by the construction of a large section rectangular top pipe tunnel crossing mixed strata, finite difference software was used to analyze the surface settlement characteristics caused by the construction of a large section rectangular top pipe in five different spatial combinations of soft and hard strata, the numerical calculations results were compared with measured data, and the results were compared and analyzed with on-site measurements. By demonstrating the influence of soil layer thickness on surface settlement deformation in the combination of upper soft and lower hard strata, a modified nonlinear model was introduced to quantify the effect of soft and hard soil layer thickness on the width coefficient of settlement troughs. The main conclusions are as follows, (1) The surface settlement value increases with the proportion of the soft layer, and the deformation mainly occurs in the upper soft soil layer, and the settlement groove shape extends to both sides of the surface in a “V” shape. (2) The maximum surface subsidence is approximately linearly related to the proportion of soft soil layers, while the width coefficient of the settlement trough is non-linearly related to the proportion of soft soil layers in the cross-section. The modified nonlinear formula characterizes the influence of each soil layer on the width coefficient of the settlement trough in the combination of upper soft and lower hard strata. The coefficients of the upper soft soil layer and the lower hard soil layer are 0.475 and 0.95, 0.26 and 1.1, respectively.