Abstract: The pile cap of 888#pier of Beichen Bridge has large foundation pit depth,complex geological conditions and great difference in soil thickness around the pit.Due to the tight construction period,combined with a variety of factors for analysis,the large diameter locking steel pipe pile cofferdam scheme is finally selected.The locking form of steel pipe pile is optimized,and the locking form of square pipe and I-beam is adopted.At the same time,in order to prevent water seepage in deep pits,fiber bag grouting measures are adopted in the locking mouth.In addition,in order to obtain the actual working state of the cofferdam,the simulative calculation of the main structure of the cofferdam was carried out using the Venus Foundation pit software.The calculation results show that the stress,displacement and stability of the cofferdam structure all meet the requirements.The deformation is highly consistent with the calculated value,indicating that the calculation of the cofferdam is accurate and reliable.Construction practice shows that the optimized lock form combined with the lock grouting measures has a good water stop effect during the support of the 11mdeep water foundation pit,which ensures the smooth operation of the foundation pit bottom sealing and the construction of the bearing platform.

摘要： 北辰特大桥888号桥墩承台位置的基坑深度大、地质条件复杂、坑周土层厚度差异较大,且工期紧张,结合多种因素进行分析,最终选取了大直径锁口钢管桩围堰方案,优化了钢管桩的锁口形式,采用了方管和工字钢的锁口形式,同时为了防止深坑渗水,在锁口内采用了纤维袋注浆措施。此外,为了获得围堰的实际工作状态,采用了启明星基坑软件对围堰主体结构进行了仿真计算,计算结果表明:围堰结构的应力、位移、稳定性均满足要求,实测围堰的变形与计算值高度吻合,表明对围堰的计算准确可靠。施工实践表明,优化的锁口形式结合锁口注浆措施,在11m的深水基坑支护过程中,止水效果良好,保证了基坑封底作业和承台施工的顺利进行。

关键词: 深水基坑, 锁口钢管桩, 锁口处理, 设计与计算