富阳地区软土深基坑施工问题分析及应对措施

Problems and corresponding solutions in construction of soft soil deep foundation pits in Fuyang area

本基坑地处杭州市富阳区中心城区,基坑挖深及影响范围内为深厚软土地层,周边环绕着地铁盾构区间、城市道路、居民小区,分布着各类城市管线,周边环境较为复杂。结合基坑特点,主要从周边环境较为复杂、承压水位高、淤泥质土层深厚等方面考虑,基坑支护结构设计采用“分区顺作+围护桩+支撑”的方案。设计单位综合考虑了基坑安全、施工工期及造价等因素,不同基坑区域采用了不同的围护桩型。在基坑开挖施工过程中,出现了立柱下沉、南侧地面局部出现裂缝等现象,及时地采取了加固措施:比如在已经下沉的立柱旁新打立柱,对立柱下沉区域内的其他立柱进行与工程桩的焊接加强,防止立柱的进一步下沉;增加预应力型钢支撑的预加轴力,增设型钢换撑来减少周边土体的位移影响,从而使问题得到了有效解决。此类应急加固措施可为类似工程提供参考借鉴。

In the central area of Fuyang District,Hangzhou City,the excavation of the foundation pit was located in a deep soft soil layer.The pit was surrounded by subway shield tunnels,urban roads,residential communities,and various urban pipelines.Considering the main characteristics of the foundation pit,including the complex surrounding environment,high confined water level,and deep silty soil layer,the design of the foundation pit retaining structure adopted a support system scheme of zoned sequential construction+retaining piles+support.The design unit comprehensively considered factors such as foundation pit safety,construction period,cost,and then adopted different types of retaining piles in different foundation pit areas.During the excavation,phenomena such as column sinking and local cracks on the ground on the south side were observed.Timely reinforcement measures were taken,such as driving new columns next to the existing sunken ones,welding and strengthening other columns in the sinking area with engineering piles to prevent further columns sinking,increasing the precompression of prestressed section steel supports and adding section steel for support replacement to reduce the displacement impact of surrounding soil.Finally,the problem has been effectively resolved by there measures,and can provide a reference for similar projects.