济南土岩组合地层地铁车站深基坑变形特性研究

Study on Deformation Characteristics of Deep Foundation Excavation in Strata with Soil⁃rock Combination in Jinan

以济南市土岩组合地层深基坑实时变形监测数据为对象,深入研究不同围护结构变形时空演化特征,并与有限元分析结果进行对比,研究表明:①吊脚桩和放坡+嵌岩桩围护体系的桩体水平位移与周边地表沉降皆主要发生于土岩结合面以上的土体范围内,岩层嵌固作用导致桩底向基坑内外的水平位移较小;②多级放坡和放坡+嵌岩桩地表沉降呈现渐缓式演化规律,即靠近基坑边缘部分沉降较大,随着距离增大而减小,吊脚桩地表沉降为勺子形,即呈先增加后减小趋势;③吊脚桩+预应力锚索围护开挖影响严重区最大(为1.0~1.1倍开挖高度),放坡+嵌岩桩次之(为0.5~0.6倍开挖高度),分级放坡+喷锚支护相对最小(为0.35~0.4倍开挖高度)。

The spatiotemporal evolution law of deformation of the deep foundation excavation in the soil⁃rock combination stratum in Jinan is studied,and compared with the existing finite element numerical analysis results.It can be shown that the horizontal displacement of the pile and the ground settlement mainly occur within the soil depth range above the soil⁃rock interface,regardless of the supporting system of the end⁃suspended pile or the rock⁃socketed pile with grading slope.The horizontal displacement of the pile bottom is very small due to the embedding of the lower rock layer.The small displacement of the end⁃suspended pile bottom tends to develop towards the foundation excavation due to the limited size of the reserved rock shoulder.Contrastly,the horizontal displacement of the rock⁃socketed pile bottom would move outside the foundation excavation.The excavation impact areas of soil and rock combination foundation excavations can be divided into three ones,including the severe impact area,the general impact area and the weak impact area.Foundation excavation construction with the end⁃suspended pile would result in the largest impact area,the rock⁃socketed pile with grading slope is the second,and the grading is relatively the smallest.