Deformation Under Dewatering And Excavation Of Deep Foundation Pit In Changzhou Metro Transfer Station

Construction conditions in and around Metro transfer stations are normally very complex.As they are surrounded by lots of buildings and pipelines,the traffic volume of which is also very large around these stations.The No.1 Metro Line of Changzhou is the largest construction project in Changzhou city.Its geological conditions are quite complex,with unconfined water,widely distributed deep confined aquifers,as well as unstable soft soil layers.Furthermore,the ground settlement and deformations around deep excavation area are hard to control.The environmental soil failure is more likely to occur in these area,which will lead to high risks to workers during the deep excavation construction.Deep excavation is one of the key links in the construction of rail transit.Therefore,it is necessary to study the deformations under dewatering and excavation process of deep excavation pit in ChangzhouMetro transfer station.This paper is based on the XinQu Park metro station of the No.1 Metro Line in Changzhou,focusing on the deformation under deep excavation and dewatering,and the excavation and dewatering effect on the deformation of surrounding buildings.The main research achievements are as follows.(1)The the deformations of the ground and surround buildings affected by dewatering and excavation process as well as their domestic control standards are summarized.(2)The general situation and geological conditions of the XinQu Park metro station are summarized.The supporting and dewatering scheme are designed in view of the arge area,the thick but weak ground layers,the deep confined aquifers and the surrounding buildings of the XinQu Park metro station.The structure and stability of the station are calculated as well.(3)A three dimensional numerical simulation model is established based on the fluid-structure coupling effect and a modified Cam-clay model of ABAQUS.The deformation under excavation and foundation are summarized.The excavation deformation considered in this model includes ground subsidence,soil horizontal displacements,underground continual wall horizontal displacements and bottom upheaval.The foundation deformation considered here includes the settlement and of horizontal displacements of the top of the pile foundation and the raft foundation.(4)The impact of different factors on the excavation deformation is analyzed.The factors used include constitutive models,poisons' ratio,void ratio,modified Cam-clay model main parameters(compression curve slope,rebound curve slope and critical state parameter),Mohr-Coulomb model main parameters(elastic modulus,friction Angle and cohesive force),contact parameters(contact friction coefficient and the limit friction resistance)and different design conditions(pillar piles,dewatering,stiffness and insertion ratio of underground continual wall and stiffness and prestress of inner support).In addition,the impact of the pile length(or the raft foundation length),the distance of foundation and foundation pit and upper load on the foundation deformation is summarized.