| The aggregation effect of subway traffic on commerce,personnel,housing and various supporting industries is becoming increasingly prominent.It can not only optimize the vertical structure of urban space,but also save land resources on the ground and promote the rapid development of the city.At the same time,a large number of foundation pit projects are located in the bustling city center.When the foundation pit is excavated,the bottom of the foundation pit will be uplifted,the horizontal displacement of the retaining structure will occur,and the settlement of the surrounding soil will occur,resulting in the displacement change of the adjacent tunnel.Bringing a series of social and environmental problems has become the focus of current urban construction and development research.Based on a large foundation pit excavation project in Suzhou,according to the influence of foundation pit excavation on adjacent tunnels,this paper widely understands the theoretical results and research status at home and abroad,as the guiding role of this research topic in related theory.Using MIDAS GTS NX finite element software numerical simulation analysis and field monitoring data analysis method,considering the displacement and deformation of retaining structure in the process of deep foundation pit excavation construction,the influence of surface settlement on adjacent tunnel is analyzed and qualitatively and quantitatively evaluated.In order to effectively control the deformation of the tunnel,the excavation sequence,the thickness of the diaphragm wall,the reinforcement width and the internal support strength of the foundation pit are studied and analyzed.The specific research contents and conclusions are as follows :（1）Through the simulation of the influence of the excavation of the foundation pit on the adjacent tunnel,it is found that since the foundation pit is divided into three small excavations,it is excavated in sequence from far to near according to the distance from the tunnel.The excavation of each foundation pit affects each other and jointly determines the deformation of the foundation pit structure and the tunnel.At the end of excavation of foundation pit 1 and 2,the inverted triangle deformation of foundation pit 3 retaining structure occurs,and the maximum horizontal displacement is 4.78 mm.At the end of excavation of foundation pit 3,the maximum deformation of foundation pit 3 retaining structure is 9.02 mm,which is in line with the classical concave deformation.At the end of excavation of foundation pits 1 and 2,the settlement trend of the outer surface of foundation pit 3 is also inverted triangle settlement,and the maximum settlement value is close to the retaining structure,and the maximum settlement value is 3.42 mm.At the end of excavation of foundation pit 3,the settlement of the outer surface of foundation pit 3 is groove settlement,and the maximum settlement value is 4.8mm.（2）Through the simulation of the influence of excavation on adjacent tunnels,it is found that due to the irregularity of foundation pit and the unevenness of excavation area,the deformation effect of double parallel tunnels is different.The up-line tunnel has an obvious inflection point near the-25 node,and the maximum displacement of the tunnel is right.The down-line tunnel is far away from the foundation pit,and the size effect of the foundation pit has relatively small influence on it.In the excavation process,the deformation effect of foundation pit 1 on the tunnel is the most obvious.The excavation of foundation pit 2 mainly affects the tunnel displacement deformation within the range of（-110,0）,and the excavation of foundation pit 3 mainly affects the tunnel displacement deformation within the range of（-25,110）.（3）The numerical simulation results are verified by field monitoring data.The monitoring data are affected by many factors,and the numerical simulation process is relatively simplified,resulting in large field monitoring data.However,the deformation laws of the two are roughly the same,which can reflect the actual deformation of the foundation pit and the tunnel.（4）The relationship between the deformation of the tunnel and the factors such as the thickness of the retaining structure,excavation method,reinforcement width,and internal support strength is studied.When the thickness of retaining structure is from 0.8m to 1.4m,the maximum horizontal displacement decreases by 11.81% and the maximum vertical displacement decreases by 14.30%;compared with the overall excavation,the maximum horizontal displacement of symmetrical excavation decreases by 18.15%,and the maximum vertical displacement decreases by 13.62%;When the width of soil reinforcement is 3m to 12 m,the maximum horizontal displacement decreases by 15.40%,and the maximum vertical displacement decreases by 17.25%.When the internal support strength was from 0.5K to 2.0K,the maximum horizontal displacement decreased by 36.92%and the maximum vertical displacement decreased by 41.49%;the optimization effect of foundation pit 3 is the most obvious for tunnel deformation control,and the corresponding tunnel protection measures are proposed.Figure [91] table [23] reference [60]... |
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