条形底板地连墙基坑斜撑段倒撑必要性研究
杨开武1,2罗正高3蒋明伟1,2祝建勋3杨春阳3
Necessity of Inverted Supports in the Inclined Strut Section of the Foundation Pit with Strip Bottom Plate and Diaphragm Wall
YANG Kaiwu1,2LUO Zhenggao3JIANG Mingwei1,2ZHU Jianxun3YANG Chunyang3
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作者信息:1.北京市轨道交通建设管理有限公司， 100065， 北京
2.城市轨道交通全自动运行系统与安全监控北京市重点实验室 100065， 北京
3.北京安捷工程咨询有限公司， 100050， 北京
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Affiliation:1.Beijing Municipal Rail Transit Construction Management Co., Ltd., 100065, Beijing, China
2.Beijing Key Laboratory of Fully Automatic Operation and Safety Monitoring for Urban Rail Transit, 100065, Beijing, China
3.Beijing Agile-Tech Engineering Consultants Co., Ltd., 100050, Beijing, China
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关键词:
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Key words:
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DOI:10.16037/j.1007-869x.2025.05.029
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中图分类号/CLCN:TV552.4+2∶U231.3
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栏目/Col:土建工程
摘要:
［目的］为节约工程投资，部分基坑斜撑段采用未完全封闭的条形底板进行基坑封底，拆除这类基坑的最下部支撑后，地连墙会发生较大突变。需研究条形底板地连墙基坑斜撑段倒撑施作的必要性及不同倒撑的基坑变形控制效果。［方法］以北京地铁某拆撑后未施作倒撑且围护结构产生变形预警的基坑为案例，通过监测数据分析拆撑后该基坑围护结构变形情况，结合数值模拟研究不同类型倒撑对该基坑变形的控制效果。［结果及结论］超宽薄壁地连墙基坑斜撑段拆撑后，基坑变形超过设计阈值，对这类基坑必须规范施作倒撑；水平倒撑和斜倒撑的基坑变形率分别为0.078和0.366，变形量相差4.68倍，水平倒撑的变形控制效果明显优于斜倒撑的；满堂红脚手架作为倒撑替代方案，该类基坑变形率为0.166，效果优于斜倒撑的而弱于水平倒撑的；不同类型倒撑中，仅水平倒撑和满堂红脚手架可将拆撑后基坑变形控制在设计阈值内；完全封闭的底板结构在基坑拆撑受力转换阶段作用充分，基坑变形率为0.304。
Abstracts:
［Objective］In order to save project investment, strip bottom plates that are not fully closed are used for the foundation pit bottom sealing in some foundation pit inclined strut sections. After the removal of the lowest supports in such foundation pits, there will be a large abrupt change in the diaphragm wall. It is necessary to study the necessity of constructing the inverted support in foundation pit inclined strut sections with diaphragm wall and strip bottom plates, and the deformation control effects of the foundation pits with different inverted supports. ［Method］In a case study of a metro line foundation pit in Beijing without inverted support after the support removal, an early warning of the retaining structure deformation occurred. The deformation of the retaining structure of the foundation pit after the support removal is analyzed through the monitoring data. Based on numerical simulation, the deformation control effects of different inverted support types on the foundation pit are studied. ［Result & Conclusion］After the support removal in the inclined strut section of the foundation pit with an ultra-wide and thin-walled diaphragm wall, the deformation of the foundation pit exceeds the design threshold. For such foundation pits, it is necessary to standardize the construction of the inverted support. The deformation rates of the foundation pits with horizontal inverted support and inclined inverted support are 0.078 and 0.366 respectively, which differ by 4.68 times. The deformation control effect of the horizontal inverted support is significantly better than that of the inclined one. When the full-height scaffold is used as an alternative scheme for the inverted support, the foundation pit deformation rate is 0.166, with a better effect than that of the inclined inverted support but weaker than that of the horizontal inverted support. Among different types of inverted supports, only the horizontal one and the full-height scaffold can control the deformation of the foundation pit after the support removal within the design threshold. The fully closed bottom plate structure produces sufficient effects in the stress conversion stage of the foundation pit after the support removal, and the deformation rate of the foundation pit is 0.304.
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