基坑开挖对邻近高铁路基变形影响的预测方法研究

依托软土地区某典型基坑工程,研究基坑开挖对邻近高铁路基变形影响的预测方法。结合该工程土体修正摩尔–库伦模型参数,建立96个不同工况下的有限元模型。通过对有限元计算结果的分析和拟合,推导能够综合考虑基坑开挖深度、支撑系统刚度和基坑距路基坡脚距离3个因素的高铁路基最大水平位移和最大沉降的简化计算公式,提出受基坑开挖影响的路基水平位移、沉降的预测曲线,并给出相应的预测流程。结果表明:在双对数坐标中,当基坑距路基坡脚距离相同时,路基最大水平位移与开挖深度的比值(δhmax/H)、路基最大沉降与开挖深度的比值(δvmax/H)均与支撑系统刚度ρ基本呈线性关系;可用图10中的折线ABC、图13中的折线DEFG分别预测路基水平位移、路基沉降;简化分析方法能较好地预测软土地区类似依托工程土层条件下受基坑开挖影响的高铁路基变形。

Study on Prediction of the Influence of Foundation Pit Excavation on Deformation of Adjacent High-speed Railway Subgrade

Focusing on a foundation pit engineering project in soft soil area,the method for the prediction of the influence of the excavation on deformation of adjacent high-speed railway subgrade is studied.This paper builds 96 finite element models for different engineering conditions using the parameters of the Modified Mohr-Coulomb model for the soil of this area.Based on the analysis and fitting of the finite element calculating results,simplified calculation formulae for the maximum horizontal displacement and the maximum settlement of HSR subgrade are worked out,which comprehensively involves three factors including the depth of excavation,the stiffness of the support system and the distance between the foundation pit and the subgrade.Prediction curves of horizontal displacement and settlement of HSR subgrade are proposed,and the corresponding prediction processes are given.The results show that according to the double logarithmic coordinates,δhmax/H(the maximum horizontal displacement of the subgrade/the excavation depth) and ρ(the stiffness of the support system) exhibit a linear relationship,so does δvmax/H(the maximum settlement of the subgrade/the excavation depth) and ρ,provided that the distance between the foundation pit and the subgrade is fixed.The horizontal displacement and the settlement of the subgrade can be calculated according to the broken line ABC in Fig.10 and the line DEFG in Fig.13 respectively.The proposed prediction method is effective in predicting the deformation of HSR subgrade in similar soft soil area under the influence of foundation pit excavation.