城市中心地带地铁深基坑开挖对周边环境影响实测分析

为研究在城市中心地带开挖地铁深基坑对邻近高架桥墩、复杂市政管线等周边环境的影响特征,以厦门轨道交通1号线城市广场站深基坑工程为例,通过对围护桩沿深度的水平位移、内支撑的轴力、坑外地下水位的变化、坑外地表沉降、周边地下管线沉降、邻近高架桥桥墩基础的沉降等进行现场监测,得出了一些有价值的结论。监测表明:桩身水平位移曲线呈典型的"内凸型";第一道钢筋混凝土支撑轴力最大,距底板最近的第四道钢支撑轴力最小;地表沉降呈现凹槽形和三角形两种沉降形态,表现出了非对称性,在坑内施作底板之后地表沉降趋于收敛;受基坑开挖影响最大的管线并不一定是距离基坑最近的,其变形量受到坑外地表沉降槽形状及最大沉降位置的影响,同时也与截面尺寸、材质、刚度等有关。高架桥桥墩基础受基坑开挖扰动较小,变化很小。

Monitoring Analysis of Effects of Subway Deep Excavationon Surroundings in City Heartland

Deep excavation in the city central area, where full of buildings and infrastructures, can cause negative impact even damage to the adjacent foundations and buried pipelines. To deeply investigate the excavation effects on the surroundings, considering the deep excavation of city Square station on Xiamen subway line 1, a large amount of field measurements including horizontal displacement of supporting pile, brace axial force, underground watertable, pipeline settlement and bridge pier movement, are analyzed thoroughly andcarefully which arrive at some valuable conclusions. The results show that: (1)the supporting pile presents a bulging deflection; (2) the maximum axial forceof inner brace appears in the top reinforced concrete ones, while the minimum appears in the bottom ones; (3) the surrounding surface settlement profiles show asymmetrical distribution, with concave type on one side and spandrel type on theother, and the settlements tend to convergence after pouring the bottom plate;(4) the buried pipelines which suffers the greatest impact from the excavation isnot the nearest one, but is about the ground settlement profile and the locationof the maximum settlement as well as the cross section size, material and stiffness of the pipeline; and (5) the foundations of viaduct pier get little disturbance from the excavation with small settlements.