Study On Support And Dewatering Schemes For Super Large Irregular Foundation Pit Under Complex Geological Conditions

Support and dewatering of foundation pit is a complex geotechnical engineering problem,it is complex and systematic,it is the key to improve the quality of the project and reduce the accident.It involves safety,economy,environmental protection,construction time,sustainable development and so on.In recent years,underground construction has been increasing in the lower reaches of the Yangtze River.The pit is characterized by deep excavation,large scale and complex shape.Because the geological and environmental condition is very complex in this area,the support and dewatering of the foundation pit are very difficult.It is an important technical issues how to fully understand the basis of the geological and environmental condition of foundation pitand design on structure safety,economy reasonable,feasible construction excavation and dewatering schemein the field of geotechnical engineering.The research work of this paper is based on the project of close to the Yangtze River underground multilayer transportation hub project of Nanjing Youth Olympic axis:(1)In order to facilitate the engineering design and construction personnel to better grasp and understand the site engineering geological conditions,the geological layer group had been divided by analyzing the rock characteristics and rock and soil physical and mechanical properties of the ground layer in the field area.The geological characteristics had been comprehensively analyzed,and the main engineering geological problems were given.The whole venue for the uneven foundation,foundation stability,existence of piping,adverse geological phenomena such as soil loss.It has a great influence on the construction safety.(2)According to the different excavation depth,the engineering geological condition and the surrounding environment of the excavation area in the core area of the B2-J1 District,the horizontal division and vertical delamination had been studied,so as to facilitate the design and construction.The area had been divided into a area,B area and C area on the plane,vertically divided into ?,?,?,?.According to the above several main factors,the supporting structure scheme of the area had been analyzed and optimized.Finally,the supporting structure had been calculated by the software of Lizheng deep foundation pit.The stability of the retaining structure had been checked according to standard.(3)The foundation pit dewatering principle,key technology and method of filter tube structure of dewatering well had been studied.According to different excavation depth and enclosure structure,the dewatering design of foundation pit in different sections had been designed.Finally,that ground deformation caused by dewatering was controlled with recharge technological method in J3 area.This design of foundation pit supporting and dewatering had been successfully applied to the project,and which had ensured effectively and smoothly on the whole project.