软土地区支护墙平面及空间变形特性与开挖环境效应分析

发布时间：2018-06-10 07:55

本文选题：基坑 + 围护结构　；参考：《浙江大学》2015年博士论文

【摘要】：随着城市化进程的加快以及对城市空间利用要求的不断提高,目前的基坑工程也呈现出一些新的问题,基坑工程呈现出开挖规模大、挖深大以及基坑周围环境复杂的特点。为了更好的控制周围既有设施的安全,对地下开挖工程的围护结构变形的要求也越来越高。同时,对基坑开挖引起的周围设施的变形预测以及保护措施的研究也具有重要的现实意义。本文结合杭州地区的现场试验、数值模拟以及理论分析对基坑工程的变形特性以及基坑开挖对周围既有设施的变形影响进行了分析,主要研究工作及创新成果如下： 1、对软土地区常见的三种基坑围护结构：排桩加止水帷幕结合内支撑围护结构、SwM工法桩结合内支撑围护结构、地下连续墙结合内支撑围护结构的侧向位移、桩(墙)后地表沉降、深层土体沉降等变形特性进行了对比分析,分析表明不同类型围护结构的侧向变形以及土体沉降变化趋势较为接近,而围护结构的系统刚度对围护结构及周围土体的变形值影响较大。 2、嵌岩连续墙由于端部处于强度较高的岩层中,其围护性状不同于连续墙端部处于土层时的围护性状。通过对嵌岩连续墙和非嵌岩连续墙的侧向位移、竖向位移、支撑轴力等监测资料的分析对比发现,嵌岩部分连续墙的最大侧向位移小于非嵌岩部分连续墙的最大侧向位移。随着连续墙系统刚度的提高,墙身侧向位移呈减小的趋势,嵌岩部分连续墙最大侧向位移的减小幅度小于非嵌岩部分侧向位移的减小幅度。非嵌岩连续墙在第一道混凝土支撑和第四道钢支撑上的支撑轴力要远大于嵌岩连续墙,且支撑轴力总和比非嵌岩连续墙大44.9%。 3、结合一双排微型桩的现场试验,分析了双排微型桩围护结构控制变形的作用机理。后排桩所受主动土压力、基坑底部所受被动区土压力和桩身位移有关,被动区的实测土压力和弹性地基梁法计算值比较接近。 4、具有内支撑围护结构的系统在基坑边角处具有更大的系统刚度,使得基坑边角附近处土体的位移小于距离边角较远处土体的位移,即基坑的变形问题表现出三维特性。通过对不同类型围护结构现场监测资料的分析发现,不同类型围护结构变形及周围土体沉降的三维效应有所不同,土体沉降和侧向位移的三维效应有一定的相关性。 5、根据围护结构周围土体变形的特点,给出了建筑沉降的计算方法并结合实测结果进行了对比验证。同时,根据实测资料,分别分析了基坑开挖引起的建筑沉降、管道沉降的变形特点,并给出了管道、建筑沉降与地表沉降的关系。 6、通过数值模拟分析提出了周围受荷桩基存在时的土体侧向位移及土体沉降规律的简化计算方法。同时对桩间距及承台间距等参数对土体沉降及侧向位移的影响进行了分析,分析结果表明,受荷桩的存在导致桩周的土体侧向位移变大,增加系数为1.0-1.3倍；土体沉降会有一定程度的减小,折减系数可以根据经验公式求得。本文也对基坑开挖引起的土体沉降对既有受荷桩基侧阻及端阻的影响进行了分析,并分别提出了适合于摩擦桩及端承桩的建筑沉降简化计算方法并与工程实测数据进行了验证。同时,也提出了基坑开挖引起的建筑侧向位移的计算方法。
[Abstract]:Along with the acceleration of urbanization and the increasing demand for urban space utilization , the foundation pit engineering presents some new problems . The foundation pit engineering has the characteristics of large excavation scale , large excavation depth and complex surrounding environment . In order to better control the safety of existing facilities around the foundation pit , the requirements for deformation of surrounding structures of underground excavation engineering are also higher and higher . At the same time , the research on deformation prediction and protective measures of surrounding facilities caused by excavation of foundation pit also has important practical significance .

Based on the field test , numerical simulation and theoretical analysis of Hangzhou area , the deformation characteristics of foundation pit engineering and the influence of foundation pit excavation on the deformation of existing facilities around the foundation pit are analyzed . The main research work and innovation results are as follows :

1 . Three kinds of foundation pit enclosure structures common in soft soil area are as follows : pile row and water stop curtain combined with inner support enclosing structure , SwM working method pile combined with inner support enclosing structure , lateral displacement of pile ( wall ) , surface settlement after pile ( wall ) and settlement of deep soil , etc . The analysis shows that the lateral deformation of different types of surrounding structures and the tendency of settlement of soil mass are close to each other , and the system rigidity of enclosure structure has great influence on the surrounding structure and the deformation value of surrounding soil .

2 . In the rock - socketed continuous wall , the maximum lateral displacement of the continuous wall of the rock - socketed part is less than the maximum lateral displacement of the continuous wall of the non - socketed part because the end part is in the rock stratum with higher strength , and the maximum lateral displacement of the continuous wall of the rock - socketed part is less than the maximum lateral displacement of the discontinuous wall of the non - socketed part .

3 . Combined with the on - site test of a double - row micro - pile , the mechanism of controlling deformation of the double - row micro - pile enclosure structure is analyzed . The active earth pressure of the rear row pile , the soil pressure at the bottom of the foundation pit and the displacement of the pile body are concerned , and the measured soil pressure in the passive area is close to the calculated value of the elastic foundation beam method .

4 . The system with built - in support structure has greater system rigidity at the corner of the foundation pit , so that the displacement of the soil around the corner of the foundation pit is less than the displacement of the soil around the boundary angle , that is , the deformation problem of the foundation pit shows the three - dimensional characteristic . Through the analysis of the field monitoring data of different types of enclosure structures , the three - dimensional effect of deformation of different types of enclosure structures and settlement of surrounding soil is different , and the three - dimensional effect of settlement and lateral displacement of the soil has a certain correlation .

5 . According to the characteristics of the deformation of the soil around the surrounding structure , the calculation method of the building settlement is given and compared with the measured results . At the same time , according to the measured data , the deformation characteristics of the settlement and the settlement of the pipeline caused by the excavation of the foundation pit are analyzed , and the relation between the settlement of the pipeline and the surface subsidence is given .

6 . A simplified calculation method for the lateral displacement of soil and the rule of settlement of soil mass is presented by numerical simulation analysis . The influence of pile spacing and spacing of bearing platform on settlement and lateral displacement of soil mass is analyzed . The results show that the lateral displacement of soil body caused by the existence of pile is 1.0 - 1.3 times .
The settlement of soil mass can be reduced to some extent , and the reduction coefficient can be obtained according to the empirical formula . In this paper , the influence of settlement of soil mass caused by excavation of foundation pit on both side resistance and end resistance of the existing pile foundation is analyzed , and the simplified calculation method of building settlement suitable for friction pile and end - bearing pile is also presented .
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU473

【参考文献】