深基坑工程施工变形监测与数值模拟对比分析研究

Comparative analysis and research on deformation monitoring and numerical simulation for deep foundation pit engineering

以天津市某深基坑工程为背景,对现场监测数据进行整理、分析,并采用PLAXIS 3D有限元数值模拟分析法建立三维空间实体模型,对基坑开挖施工过程中地连墙深层水平位移以及周边地表沉降进行数值模拟分析,将监测数据与模拟计算结果进行对比分析,研究结果表明,数值模拟结果与现场实测数据变化趋势基本一致,数值较接近,地连墙深层水平位移相差3 mm以内,周边地表沉降相差4 mm以内;随着开挖深度的增加,地连墙深层水平位移逐渐增大,且最大位移点逐渐下移,墙体位移变化呈中间大、两端小的"鼓肚"形状;随着土方开挖的进行,周边地表沉降逐渐增大,最大沉降值点逐渐向基坑外侧延伸,在第四步土方开挖完毕及基坑顶部施工完成后,最大值点均出现在距基坑边11 m处;实测值与计算值均在规范限制以内,符合基坑变形要求。

Based on a deep foundation pit project in Tianjin,through collection and analysis of the field monitoring data,PLAXIS 3 D finite element numerical simulation analysis method is used to establish a 3 D spatial entity model to simulate the deep horizontal displacement of diaphragm wall and surrounding surface subsidence in the process of foundation pit excavation,and the monitoring data and simulation results are compared and analyzed in this paper.The results of the foresaid study and analysis show that the results of numerical simulation is consistent with the change trend of actual field measured data and the difference of horizontal displacement between them is within 3 mm,and the difference of surrounding surface subsidence between them is within 4 mm. With the increase of excavation depth,the deep horizontal displacement of diaphragm wall is increasing gradually,and the maximum displacement point gradually moves down,the change of the wall displacement appears in a shape of ＂bulging belly＂as large in middle and small in ends.With the excavation of the earthwork,the surrounding surface subsidence gradually increase,the maximum settlement point is gradually extending towards outside of the foundation pit.When the fourth step＇s earthwork excavation and foundation pit top construction are finished,the maximum point is 11 m far away from base pit. Both measured and calculated values are within the specification limits,and both satisfy the requirement of foundation pit deformation.