系列超深超大基坑群设计实践与探索

妥善解决周边环境保护和施工相互影响问题是确保基坑群工程安全经济的关键。系统归纳基坑群分类、工程设计施工重难点及解决措施,依托广州复杂超深超大基坑群工程,开展不同建设模式的方案对比,结合具体工况重点探讨建设过程中的重难点,并针对性提出解决方案。结果表明:基坑群工程在理论技术层面需重点关注群坑效应;基坑群设计应合理安排施工顺序,分区、间隔、对称开挖,支护体系加载卸荷的传力路径应清晰。在超深超大基坑群工程中,为保护周边建筑,先开挖远侧坑,创新利用八字撑和主撑轮换受力实现接撑及支顶传力;集束群锚设计可解决部分地段常规桩锚施工难的问题;地块独立实施结合局部合并的建设模式能较好解决整体合并开发模式相互制约大、进度慢的问题;根据现场建筑的实际拆迁进度,运用先化整为零后组合的思路,采用基坑群分坑动态设计结合建筑物逐个孤岛保护的方案进行分期施工。

Design Practice and Exploration of Several Ultra-Large Ultra-DeepFoundation Pit Groups

The key to ensure the safety and economy of foundation pit group engineering is properly solving the problems of surrounding environmental protection and construction interaction. This paper systematically summarizes the classification of foundation pit group, the key and difficult points of engineering design and construction, and the corresponding solutions. Relying on the complex ultra-large deep foundation pit group project in Guangzhou, the scheme comparison of different construction modes is carried out, the key and difficult points in the construction process of each complex foundation pit group project are mainly discussed combined with the specific working conditions, and corresponding solutions are put forward. The results show that the effect of group pits should be paid more attention in theory and technology of foundation pit group engineering. In the design of foundation pit group, the construction sequence should be reasonably arranged, and the excavation should be carried out in different zones, intervals and symmetrically. The loading and unloading path of support system should be clear. In the ultra-large deep foundation pit group project, in order to protect the surrounding buildings, the far side pit is excavated first, and the eight shaped brace and the main brace are used to bear the force alternately to realize the connection of the brace and the force transmission from the top of the brace. The design of cluster anchor group can solve the problem of difficult construction of conventional pile anchor in some sections. The construction mode of land independent implementation combined with local consolidation can better solve the problems of mutual restriction and slow progress of the overall consolidation development mode. According to the actual demolition progress of the building on site, combined with the idea of drawing the whole first and then combining, the scheme of dynamic design of each pit in foundation pit group and buildings adopt island protection one by one is adopted for phased construction.