Research On Foundation Pit Deformation And Key Technologies In Complex Environment

Urban subway stations are generally located in downtown areas,with many surrounding buildings,many influencing factors of people flow and traffic flow,and dense underground municipal structures.If the hydrogeological conditions are relatively complex,the foundation pit construction will face many engineering hazards.If the foundation pit instability accident occurs,it will cause huge economic benefit loss and serious adverse social impact.How to ensure the construction safety and economic applicability of deep foundation pit engineering in subway station is particularly important.Focusing on the stability and deformation of the retaining structure in the process of deep foundation pit construction,this paper takes the foundation pit of Xi ’an Road Station of Xuzhou Metro Line 1 as the background,and comprehensively adopts theoretical analysis,numerical simulation,field implementation and in-situ engineering test to study the key technologies of subway deep foundation pit construction in complex environment.The main research results are as follows:(1)The risk sources of urban subway deep foundation pit in complex environment are analyzed and evaluated,and it is found that the cohesion and gravity of surrounding soil are the main factors affecting the safety of foundation pit construction.(2)Using fuzzy mathematics theory to optimize the supporting form of subway foundation pit,the comprehensive value of evaluation model shows that diaphragm wall is the most effective supporting way for deep foundation pit construction in complex environment.(3)The horizontal deformation of the foundation pit generally intrudes into the inner side of the foundation pit,and the development of horizontal displacement is closely related to the excavation depth.With the excavation of foundation pit and the erection of each layer of support,the horizontal displacement curve of retaining structure gradually changes to bow shape,and the maximum horizontal displacement moves down with the increase of excavation depth.(4)When the plane dimension of subway foundation pit is large and the excavation depth is large,the support structure combining diaphragm wall with inner support is an effective measure for deep foundation pit support.The comprehensive support composed of crown beam,middle purlin and inner support system makes the deformation of foundation pit more complicated under the synergistic action of soil and retaining structure.(5)The horizontal displacement caused by foundation pit excavation moves in the direction without underground structures.The existence of underground structures limits the horizontal displacement of the enclosure wall,strengthens the soil,limits the movement of the soil into the pit,and leads to the smaller horizontal displacement of the enclosure.(6)When simulating the foundation pit construction,the numerical simulation method can not accurately reflect the deformation of the foundation pit,which can be used for reference,but other effective monitoring measures must be added to help ensure the safety of the foundation pit construction.There are 28 figures,13 tables and 74 references in this paper.