分期施工基坑开挖变形特征与数值模拟分析

The Second Stage Excavation Deformation Characteristics in Staged Construction and Numerical Simulation Analysis

为研究分期施工过程中二期基坑开挖变形的特性及规律,以武汉市轨道交通11号线东段工程光谷线网控制中心工程为例,通过现场监测和使用Plaxis3D数值模拟相结合的方法,分别对地表沉降、桩顶沉降、桩顶水平位移、桩体水平位移和建筑物沉降进行了数据监测和模拟最后将监测结果和模拟结果对比分析,来研究二期基坑施工过程中基坑变形特性。结果表明:基坑周围围护结构变形随着基坑开挖深度的增大呈现出隆起和沉降两种不同的变化趋势,基坑开挖到达最深处时地表沉降和围护结构的位移达到最大,最后随着基坑主体结构的完善而趋于稳定;二期基坑施工过程中基坑开挖变形最大处位于一期和二期支护结构公共处,在水平方向由支护结构公共处中心位置向两端减少,垂直方向由支护结构公共处中心位置到基坑底部变形量从大到小变化,呈现出中间大两头小的变化特征。计算分析表明数值模拟结果与现场监测结果变化趋势一致,计算数据与监测数据差距较小,为基坑工程的合理设计与安全施工提供了科学依据。

In order to study the deformation characteristics of the second stage foundation pit excavation during the staged construction process,this paper took the Optical Valley line network control center project of the east section of Wuhan rail transit line 11 as an example.Through the method of combining on site monitoring and the use of Plaxis3D numerical simulation,the ground settlement,pile top settlement,pile top horizontal displacement,pile horizontal displacement and building settlement were monitored and simulated.Finally,the monitoring results were compared with the simulation results.Analysis of the results is aimed to study the deformation characteristics of the foundation pit during the construction of the second stage foundation pit.With the increase of the excavation depth of the foundation pit,the deformation of the maintenance structure shows two different trends of uplift and settlement.When the excavation of the foundation pit reaches the deepest depth,the surface settlement and the displacement of the retaining structure reach the maximum,and finally stabilize with the improvement of the main structure of the foundation pit.During the construction of the second phase of the foundation pit,the largest deformation of the foundation pit is located at the common part of the first and second phases of the supporting structure.In the horizontal direction,it decreases from the central position of the common part of the supporting structure to both ends,and the vertical direction of the deformation from the center of the supporting structure to the bottom of the foundation pit decreases gradually,indicating that the characteristics of small changes in the middle and two ends.The numerical simulation results are consistent with the changes in the field monitoring results.The gap between the calculated data and the monitoring data is small,which provides a scientific basis for the rational design and safe construction of foundation pit projects.