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组合支护体系由上部土钉墙和下部锚拉桩(墙)结构联合形成,北京城区超过15m深的基坑越来越多地采用这种支护体系。以开挖深度约22m的北京侨福花园广场深基坑工程为例,分析了上部土钉墙在基坑开挖各阶段的内力变化规律,在开挖至土钉墙底时,土钉内力增长速率最快,当基坑潜在滑裂面超过土钉墙末端时,进一步的开挖对土钉内力增长影响有限;由于预应力锚杆的存在,减小了基坑坡顶的位移,同时土钉内力比设计值要小很多,今后类似工程设计可以减小土钉杆体直径。
The combined support system is formed by the combination of upper soil nailing wall and lower anchorage piling (wall) structure. Such a supporting system is increasingly used in the foundation pit more than 15m deep in Beijing urban area. Taking the deep foundation pit project of Beijing Qiaofu Garden Square with an excavation depth of about 22 m as an example, the internal force variation of the upper soil nailing wall in each stage of foundation pit excavation was analyzed. When excavating to the soil nailing wall, The fastest growth rate. When the potential slip surface of the foundation pit exceeds the end of the soil nailing wall, further excavation will have a limited impact on the internal force growth of the soil nail. Due to the prestressed anchor, the displacement of the top of the foundation pit is reduced, Soil nail force is much smaller than the design value, similar projects in the future can reduce the diameter of soil nail rod body.