Optimization Analysis Of Deep Foundation Pit Support Adjacent To Subway

With the rapid development of urban construction and underground space development,the surrounding environment of foundation pit projects has become increasingly complex,and some deep foundation pit projects have appeared near the operating subway.At this time,the excavation of deep foundation pits is not only related to the safety of the foundation pit itself,but also It will have a great impact on the operation of the nearby subway,which makes the design of deep foundation pits challenging.How to consider the impact of subway vehicle loads on the foundation pit support structure and control the deformation of the support structure at the same time?This problem has gradually attracted the attention of the industry and has become one of the hot issues in the field of geotechnical engineering.In this paper,taking Fanglue City Square Phase Ⅱ foundation pit support project near Changsha Metro Line 4 as the engineering background,based on the changing characteristics of subway vehicle loads,MIDAS/GTS finite element software is used to carry out numerical simulation,and systematically analyze the effect of subway vehicle load on the The deformation of the foundation pit supporting structure of Fanglue City Square Phase Ⅱ and the influence of internal force,by changing the load action mode of subway vehicles,the distance between the subway and the foundation pit,the bolt setting parameters,etc.The calculation results of different working conditions are compared and analyzed,and the deformation law of the support structure of the deep foundation pit near the operating subway is obtained,and the design of the support structure is optimized,which provides a reference for the design and construction of similar deep foundation pit projects.The following conclusions were drawn from the research:(1)The generation mechanism,influencing factors and changing characteristics of subway vehicle load are expounded,which provides a theoretical basis for numerical calculation and modeling.(2)Based on the variation characteristics of subway vehicle loads,a numerical calculation model was established.According to different vehicle running speeds and modes,the three-dimensional numerical simulation of the foundation pit was carried out,and the influence law of the subway vehicle load on the deformation and internal force of the foundation pit supporting structure was obtained.The pit support structure design has reference value.(3)Change the parameters such as the horizontal distance between the foundation pit and the subway,the spacing of the supporting piles,the inclination angle of the anchor rod,and establish a number of three-dimensional dynamic analysis models.and bending moment,as well as the change law of the earth pressure of the foundation pit supporting structure,which lays a foundation for the optimization of the foundation pit supporting structure.(4)With the increase of the horizontal distance between the foundation pit and the subway,the displacement of the soil around the foundation pit,the bending moment of the pile body and the earth pressure will decrease.When the horizontal distance between the foundation pit and the subway is greater than 10m,the foundation pit supporting structure It is less affected by the subway vehicle load;as the distance between the supporting piles decreases,the displacement of the soil around the foundation pit,the bending moment of the pile body and the earth pressure all decrease.When the distance between the supporting piles is less than 4m,the foundation pit supports The retaining structure is less affected by the spacing of the supporting piles;without affecting the subway operation and surrounding buildings,the optimal incident angle of the bolt is 25°.