深基坑与邻近建筑物相互影响的实测及数值分析

Field Measurement and Numerical Analysis of the Influences Between the Deep Excavation and Adjacent Buildings

随着近年来高层建筑的大规模建设,基坑开挖深度逐渐增大,由于深基坑通常位于城市的繁华地带,且常常紧邻各种建筑物,如何处理好基坑开挖及支护等施工过程对周边环境的影响,成为基坑工程研究的关键。以近接浅基础建筑物的桩锚支护结构深基坑为工程背景,基于现场实测数据深入分析了桩体变形、桩顶位移和建筑物沉降等变化规律,基于Plaxis有限元软件建立数值模型,经模型计算结果与现场监测数据对比选取合理的土体本构模型,探讨了邻近建筑物基础位置和地基附加应力两个关键参数对桩锚支护结构基坑与邻近建筑物本身的影响规律。研究表明:混凝土支撑和冠梁在控制围护桩顶变形的同时会增大坑角效应的影响范围;对于基坑开挖卸载问题,硬化土模型(HS模型)相对于莫尔库伦模型(MC模型)具有更准确的模拟效果;基坑施工主影响区域约围护结构后方2.5He(基坑开挖深度),建筑物平均沉降最大值和倾斜度最大值位置分别位于距围护结构约0.6He和1.1He处;建筑物平均沉降值δva最大值位置与地表沉降最大值位置吻合,倾斜度最大值位置约位于地表沉降曲线反弯点处;针对本文工程,当建筑物基础埋深为2.5 m,基坑围护桩与建筑物中心距离在7.5~52.5 m范围内变化时,建筑物平均沉降和倾斜度最大值分别约为8.3 mm和0.00025;平均每增高一层建筑物,其沉降值和倾斜度分别增加约0.9 mm和0.7×10^-4,基坑围护结构最大侧移量增加1.4~2.0 mm,其增量随层数增高而增加。

With the large-scale construction of high-rise buildings in recent years,the depth of the excavations has gradually increased.Since deep excavations are usually located in the prosperous areas of the city,and close to various buildings,how to deal with the impact of the construction process such as soil excavation and retaining structure installation on the surrounding environment has become the key issue to the research of deep excavation.The deep excavation of tieback anchored pile retaining structure near the shallow foundation building is studied in this paper.Based on the field observations,the variations of pile deformation,pile head displacement and building settlement were analyzed in detail.Numerical models were established using FEM(finite element method)program Plaxis.A reasonable soil constitutive model was selected by comparing the calculated results with the field monitoring results.Two key parameters,including the position of the adjacent building foundation and the additional stress of the foundation,were discussed,in order to obtain the disturbance behaviors between the anchored pile wall excavation and adjacent building.The research results showed that the concrete supports and the crown beam would increase the influence region of the excavation corner effect while restraining the deformation of the retaining pile head.For excavation unloading issues,the calculated results obtained from Hardening−Soil(HS)model are more accurate than those from the Mohr−Coulomb(MC)model.The primary influence zone locates at the region within 2.5He(excavation depth)behind the retaining structures.The maximums of average building settlements and building inclinations are 0.6He and 1.1He.The positions of the maximum of average building settlement and the ground surface maximum settlement are identical.The position of the maximum of inclination is located at the inflection point of the ground settlement curve.For this project,when the buried depth of the building foundation is 2.5 m and the distance between the retaining pile of the deep excavation and the center of the building changes within the range of 7.5~52.5 m,the maximums of the average settlement and inclination of the building are about 8.3 mm and 0.00025,respectively.Furthermore,for each additional floor,the settlement and inclination of buildings increase about 0.9 mm and 0.7×10^-4,respectively,and the maximum lateral displacement of the retaining structure of the deep excavation increases by 1.4~2.0 mm,of which the increment increases with the number of floors.