Research On Excavation And Deformation Law Of Deep Foundation Pit Of Subway Station Under Mountain Bias

The surrounding geological conditions of Songyuanxia Station of Shenzhen Urban Rail Transit Line 4 Phase III Project are complex.The north side of the foundation pit is adjacent to the mountain of Songyuan Park,and the south side is a sinking square constructed simultaneously,The height difference between the construction site of Songyuanxia Station and the nearby terrain is large.Under the condition of mountain bias,station foundation pit construction may cause disturbance to stratum,water loss and stratum stress loss,and the stress between slope support,station support structure and main structure is extremely complex,which is easy to cause risks such as foundation pit support instability and station structure deformation.At present,the existing codes and standards do not accurately guide the design and construction of mountain biased foundation pits for such problems.Therefore,it is of great significance to study the excavation and deformation law of deep foundation pit of subway station under mountain bias,find out the difference between it and traditional symmetrical load foundation pit,and provide experience and reference for similar engineering construction in the future.Through literature research,theoretical analysis,on-site monitoring,numerical simulation and other means,this paper has carried out relevant research on the deep foundation pit construction of mountain bias station from the following parts:(1)Through in-depth understanding of the development status of the biased foundation pit based on the existing literature,grasp the deformation law of the supporting structure of the deep foundation pit engineering,and realize the influence law of the biased pressure on the deformation of the supporting structure of the deep foundation pit.(2)Introduce the commonly used supporting methods of deep foundation pit,recognize the deformation mechanism and influencing factors of mountain bias foundation pit,and the control measures taken when subway stations face bias action,which provide theoretical basis for the excavation supporting design of bias foundation pit engineering.(3)In this paper,a three-dimensional numerical model of the mountain biased foundation pit is established by finite element calculation software.The deformation of the foundation pit retaining structure and its influence on the stability of the mountain slope at Songyuanxia Station under each excavation process are studied,as well as the influence of the biased foundation pit excavation on the surrounding surface settlement.The calculationresults show that the internal force and deformation of the supporting structure of the biased foundation pit during the excavation process are within the design allowable range.(4)Through on-site monitoring and analysis of the excavation effect of the biased deep foundation pit,and based on the on-site measured data and comparing the three-dimensional numerical calculation results,the deformation law of the supporting structure during the excavation process of the mountain biased deep foundation pit is verified.Finally,the main research results of this paper are summarized and the topic of subway deep foundation pit excavation under mountain bias is prospected.