Analysis On The Influence Of Excavation Sequence Of Deep Foundation Pit In Different Sections Of Huai'an East Station On The Envelope And Ground Settlement

Since the beginning of the new century,high-speed railways have allowed cities to achieve co-urbanization,expanded the concept of modern cities into "urban circles",balanced transportation circles and economic circles,greatly improved regional economic development,and high-speed rail stations are also maximized The basic symbol of the underground space.The stability of the station foundation pit has a significant impact on the safety of the project.The construction of deep foundation pits needs to be carried out in a complex environment.In this complex environment,it is necessary to ensure that the excavation of the foundation pit is carried out smoothly and will not damage the common.The safety and stability of the elevated high-speed rail station.This article takes the deep foundation pit project of the Huai'an East Station transportation hub as a research background,compares the actual measurement data of the project with the numerical simulation analysis of the MIDAS GTS NX finite element software,and fully combines the research achievements and theoretical foundations of previous scholars.The relevant deformation and displacement laws are summarized,and the displacement of the envelope structure and the surface settlement laws are analyzed and compared in depth during the excavation sequence of different zones.Adopting a scientific and reasonable excavation sequence plan can greatly shorten the construction period,project cost and speed up the construction progress.Through the research in this paper,we can provide a valuable reference for the next foundation pit project in Huai'an soft soil area.:(1)Introduced the deformation of the retaining structure caused by excavation of the foundation pit,the surrounding ground settlement and the uplift at the bottom of the foundation pit,and other commonly used calculation methods for the corresponding displacement.Several control measures for foundation pit deformation have been introduced;(2)The data of the key monitoring points of the foundation pit were selected and analyzed: the maximum horizontal displacement of the enclosure structure was just at the top of the pile at the beginning.There was not too much overall deformation of the enclosure structure during the initial excavation."Concave" shape,the middle and lower parts are convex,the two ends are small,the largest side is 17.74 mm,and the maximumhorizontal displacement is 8m below the ground;(3)The surface subsidence value increases first and then decreases with the distance from the edge of the foundation pit.The surface subsidence curve gradually changes from a "triangle" to a "groove",and the location of the maximum surface subsidence will slowly It is fixed at about 10 m from the edge of the foundation pit,and the maximum settlement value is 10.26mm;the axial force of the support beam and the ring brace will slowly increase,the axial force of the two layers of concrete is within the safe range,and the overall excavation of the foundation pit is in a safe and controllable situation;(4)Comparing and analyzing the data obtained from the simulation calculations and comparing with the on-site measurement values,it is found that there are some errors between the two.The excavation and support process of the foundation pit is extremely complicated.The weather,nearby construction loads and other factors interfere with the objective existence and cannot be avoided.Overall,the simulation results can accurately reflect the basic trend of foundation pit deformation;the surface settlement monitoring value around the foundation pit,Peck formula calculation value and numerical simulation value are compared and analyzed.Among them,the calculation curve of Peck theory and the numerical simulation of surface settlement effect The range is roughly the same,and the trend of the curve change is satisfied with the monitoring value as a whole,indicating that the Peck curve and the numerical model can obtain relatively high accuracy;(5)Basin excavation is adopted based on the foundation pit.Within a certain range of reserved soil width,the two indicators of surface settlement and lateral displacement of the enclosure structure will gradually decrease with the increase of the width.The reserved soil width of 40 m can be used as the optimal length of the basin excavation of the project;(6)Different excavation and unloading paths will cause differentiated deformation characteristics of the foundation pit.When the excavation sequence scheme adopts the excavation from the middle circular ring brace to the four corners of the foundation pit,the maximum horizontal lateral movement of the envelope structure is reduced by about 11%,the maximum surface settlement is reduced by about 2.46 mm,indicating that this scheme is reasonable.Figure [48] Table [6] Reference [65]...