砂质粉质黏土深基坑渗透的现场监测结果分析

In-Situ Monitoring Results Analysis of Deep Foundation Pit Penetration of Sandy Silty Clay

深圳市前海合作区滨海大道基坑底部砂质粉质黏土在雨季遇水浸泡后软化,发生渗漏、流砂险情。为此,对深基坑渗透的现场监测结果进行了分析。结果表明:(1)对砂质粉质黏土地基,基坑开挖时要避免长时间暴露,做好防排水措施。地下水的大幅度变化能很好地反映基坑渗漏水状况,底板浇筑能有效控制地下水水位以及支护桩位移的变化;(2)支撑轴力随时间发展普遍呈对数规律增大,并在基坑底板浇筑完成后有所下降。当支撑轴力随时间呈指数规律增大时,应引起重视。(3)基坑交叉或坑中坑开挖,在基坑阳角处增加背拉梁能有效提高支护结构整体稳定性,使基坑变形更协调,从而更好地保障基坑安全。

The foundation pit of Binhai road in Qianhai cooperation zone of Shenzhen is happened with leakage and flow sand and sandy silty clay softened in the rainy season after being soaked. This paper analyzes the monitoring data before and after pit penetration damage, it could be obtained that： （1）For sandy silty clay foundation, excavation must be avoided exposure for a long time and taken measures for waterproof and drainage. Significant changes in groundwater can be a good response to the foundation pit leakage conditions, the floor casting can effectively control the groundwater level and the displacement of the support pile ; （2）The axial force increases with the logarithmic rule, and decreases after the foundation pit floor pouring is finished. When the axial force increases exponentially with time, it should be paid attention to; （3）For foundation pit cross and the excavation in the pit, increasing the back straining beam at the positive angle of the foundation pit can effectively improve the overall stability of the supporting structure, so that the deformation of the foundation pit is more coordinated so as to ensure the safety of the foundation pit.