砂土地基钢格构斜向支撑桩基坑支护实例分析

Case analysis of foundation pit supporting with steel lattice oblique piles in sandy soil

本文以杭州市塘栖镇某基坑为例,基坑开挖范围内以粉砂性土为主,基坑采用PC工法组合钢管桩或拉森钢板桩作为围护体,局部降板区域采用斜向支撑桩。斜向支撑桩预施工解决了常规斜支撑土方二次开挖和底板二次浇筑的问题,可大大节省工期。同时相对于水平支撑可创造大量坑内施工空间,减少钢筋混凝土用量,降低工程造价。但是本工艺处于发展阶段,在实际项目中应用较少,此工艺依据的设计机理及施工可靠性尚不明确。本文结合工程实例,分别从斜向支撑桩的施工参数、斜向支撑桩节点、施工工艺、实际施工过程中存在的问题等多方面进行阐述。通过启明星深基坑软件计算和Plaxis二维数值模拟,并结合基坑监测数据验证斜向支撑桩在砂土地基中的可靠性。斜向支撑桩的使用可为类似砂土地基基坑设计、施工提供参考。

The project studied in this work is located in Tangqi Town,Hangzhou City,and the excavation range of the foundation pit is dominated by silty soil.The PC construction method combined steel pipe piles or Larsen steel sheet piles are used as the enclosure for the foundation pit,and oblique support piles are used in the local slab lowering area.The preconstruction of the oblique support piles solves the problems of secondary excavation of conventional oblique support earthwork and secondary pouring of bottom plates,which can greatly save the construction period.At the same time,compared with the horizontal support,it can create a lot of construction space in the pit,and reduce the amount of reinforced concrete,and also reduce the project cost.However,this process is under the development stage and it is rarely used in actual projects.The design mechanisms and construction reliability of this process are still unclear.Combined with engineering examples,this paper expounds the construction parameters of the inclined support piles,the nodes of the inclined support piles,the construction technology,and the problems existing in the actual construction process.Combined with the monitoring data of the foundation pit,the reliability of the inclined support pile in the sand foundation is verified by the calculation of the Venus deep foundation pit software and the two-dimensional numerical simulation of Plaxis.The use of oblique support piles can provide reference for the design and construction of foundation pits on similar sandy soils.