Influence of Foundation Pit Excavation and Pile Foundation Construction on Maintenance Structure Deformation

A deep foundation pit in Tongzhou, Beijing was studied as an example, the effects on the foundation pit maintenance structure and the surrounding environment were discussed including foundation pit excavation and unloading, maintenance anchor construction, CFG, and uplift pile construction. The analysis results show that: the typical maintenance structure and the surrounding surface settlement of the foundation pit float first and then decrease with the excavation of the foundation pit, maintenance of anchor cable, and construction of pile foundation. The specific performance is that the excavation unloading of foundation pit will cause the maintenance structure and the surrounding surface floating; With the increase of the excavation depth of the foundation pit, the maintenance structure and the surrounding surface begin to sink under the condition of the lateral deformation of the foundation pit and the vertical component force of anchor cable; The construction of CFG and uplift pile in the foundation pit weakens the passive earth pressure in the embedded area of the slope protection pile, dewatering in the foundation pit leads to an increase in effective stress in the soil, resulting in additional consolidation settlement, under the combined action of groundwater seepage in the foundation pit, the maintenance structure and the surrounding surface show secondary accelerated subsidence; Foundation pit excavation and foundation pile construction have little effect on horizontal displacement of pile top and axial force of anchor cable. According to the analysis results, it is suggested that increasing the embedded depth of a similar foundation pit and adjusting the piling sequence of the passive earth pressure zone will be beneficial for deformation control of the maintenance structure and surrounding environment.