Analysis Of Influence Factors Of Excavation Of Foundation Pit On Building Settlement Of Qianshan Road Of Hefei Subway

Nowadays,the subway mainly acts as the traffic hub of city to ease the traffic pressure,and subway station is generally located in the prosperous and densely populated areas of city,it is generally adjacent to existing buildings,structures,roads,underground pipelines,etc..So the construction site is complex,the protection of the surrounding environment and the existing buildings and other requirements are relatively high.Taking the Qianshan Road Station of Hefei NO.2 subway as the research object,it is comparative analyzed through on-site monitoring and numerical analysis of finite element software MIDAS/GTS simulation,they are studied that the building settlement under the influence of different factors,it mainly analyzes the influence of different supporting structures and different excavation methods on the building settlement.The main the work and achievements are as follows:(1)Describes the deformation mechanism of soil excavation and the three kinds of deformation modes,the four aspects of stability analysis of foundation pit excavation support and the four methods of calculation of ground settlement around foundation pit excavation,research shows that the settlement of the building is mainly caused by the deformation of the retaining structure and the surface settlement around the foundation pit.(2)Analyzed from the monitoring data,the settlement of the building around the pit changes with time and the settlement of the building is increasing,when the foundation pit is excavated to the deepest place,the settlement reaches the maximum value,the maximum settlement is 4.44 mm.Therefore,the amount of the settlement measured by the monitoring points around the building is in the safe range,when the settlement reaches the maximum,it will gradually slow down the rate of settlement change and gradually become stable as the construction continues.(3)The influence of foundation pit excavation on the settlement around the foundation pit can be divided into three stages: uniform settlement,differential settlement and stable settlement.From the analysis of monitoring data,it can be concluded that the location of the settlement monitoring points around the foundation pit is closer to the edge of the foundation pit,and the settlement value is larger,on the contrary,the farther the monitoring point is,the smaller the settlement value is.And thesettlement value of the settlement monitoring points of each building is within the allowable range of the settlement value of the building,the impact on the building is not obvious.(4)Simulation results of finite element software show that during the excavation of foundation pit,the maximum lateral displacement of underground continuous wall increases with the increase of excavation depth,the location of the maximum lateral displacement of the wall is located on about 10 m below the ground.Due to the excavation of the foundation pit,the underground continuous wall will gradually move into the pit,and with the increase of excavation depth the unloading of the soil will cause the increase of the pressure difference between the inner wall and the outer wall,therefore the overall displacement of the wall presents the trend of broad in the middle and small both ends.(5)The comparison between numerical simulation and field monitoring shows that,the settlement variation and trend of the buildings monitoring points arround Antian international building in the construction of foundation pit are roughly the same,the numerical results are verified.(6)Study the influence of different factors on the settlement of buildings during excavation,the selected section is simulated by MIDAS/GTS under different supporting structure and different excavation methods of foundation pit,the influence of different factors on building settlement is as follows:1)The influence of support structure of underground continuous wall on settlement of buildings is smaller than the influence of spraying pile curtain wall on settlement of buildings.First of all,in the early stage of foundation pit excavation,the construction of the jet grouting pile will cause great disturbance to the surrounding soil,so the bearing capacity of the soil will be reduced before solidification,therefore in the early stage of the foundation pit excavation,the building near the pile will produce large settlement in a short time.Secondly,in the whole process of foundation pit construction,the depth and size of foundation pit excavation are large,during the construction period,the surrounding soil will be disturbed,so in the process of building settlement will increase.Finally,when the support of foundation pit is removed,the stress load is supported by the support,so in this process building settlement will have an impact.2)The influence of excavation method of the integral excavation on the settlement of buildings is bigger than influence of central island excavation on settlement of buildings.According to the research on the excavation method,the influence of different excavation methods on adjacent buildings is significant,the center island excavation can effectively reduce the horizontal displacement of the supporting structure,the vertical settlement of the ground surface and the vertical displacement of the building,the integral excavation and the central island excavation can effectively reduce the inclination of buildings.