基于流固耦合效应的红砂岩地层深基坑围护结构变形特性分析

降水渗流引起的基坑变形问题十分复杂,采用流固耦合的数值方法,以兰州某地铁车站红砂岩深基坑为研究背景。对围护桩体水平位移、基坑内外土体竖向位移和水位变化进行现场监测,利用FLAC3D建立车站基坑降水开挖耦合模型,分析了围护结构的变形特性以及基坑内外土体竖向变形规律。结果表明围护桩体最大水平位移在0.5倍左右坑深处；基坑开挖对周围土体在0至2.5倍坑深范围内的沉降变形影响显著,最大沉降值发生在距离基坑边缘约0.55倍坑深；降水引起的基坑内外沉降随时间增加呈减小的趋势,降水与立柱桩联合作用使坑底隆起显著减小,基坑内外同时降水有利于解决红砂岩透水问题。考虑流固耦合的数值模拟与现场监测相结合预测兰州地区基坑变形更具科学性。

Analysis of Deformation Characteristics of Foundation Pit Retaining Structure in Red Sandstone Strata Based on Fluid Solid Coupling Effect

The deformation of foundation pit caused by dewatering seepage is very complicated. The fluid-solid coupling numerical method is used to study the red sandstone deep foundation pit of a subway station in Lanzhou. The deformation characteristics of the retaining pile at different depths and the variation rules of the ground settlement in the case of employing the numerical software FLAC3D to simulated the completed excavation process and monitoring the horizontal displacement of the retaining pile and the settlement of the soil around the foundation pit and are analyzed. According to the results, the maximum horizontal displacement occurs at about 0.5 times the depth of pit. The excavation of foundation pit has significant influence on the surrounding soil in the range of 0 to 2.5 times the depth of pit and the maximum settlement occurs at a distance of about 0.55 times the depth of pit from the edge of the foundation pit. The settlement inside and outside the foundation pit caused by dewatering decreases with time. The combined action of dewatering and soldier piles can reduce the uplift of the bottom of the pit significantly, and the dewatering inside and outside the pit can solve the problem of red sandstone permeability. It is more scientific to predict the deformation of foundation pit in Lanzhou area by combining numerical simulation with field monitoring.