The Analysis Of Deformation Law Of Deep Excavation In A Subway Station In Loess Areas

Design of the retaining structure and stability analysis of deep excavation in metrostation is one of the key issues in metro construction. The study on the theory of deformationlaws and monitoring of deep and long excavation has great significance. In this paper, it usesthe method that combines with the theoretical analysis, in-situ monitoring and numericalsimulation followed the background of Deep Excavation in a subway station in loess areas.The main jobs are as follows:(1)There are many factors impacting the deformation of deep excavation.They are thehydro geological conditions, the foundation size and earth pressure, design decision, therationality of the construction methods and organization. The deformation of deep excavationconsists of three parts: the wall deformation, the bottom heave of the pit and the Surroundingground settlement. The failure pattern of deep excavation contains the bow-shapeddeformation mode, the buried-type deformation mode, the forward-type deformation mode,and the kick-type deformation mode.(2) According to the geological conditions and groundwater burial conditions, combiningwith the main type of construction, it designs deep foundation pit dewatering program in asubway station in loess areas. The deep excavation is dewatered by tube well points, and itlayouts dewatering wells by the pit and precipitation observation wells in the pit.(3) The in-situ monitoring plan of deformation was designed to the Deep Excavation inthe subway station, and accomplishes the in-situ monitoring work.With the site datas,thedeformation laws of the station was analysised.it focuses on deep analysis of the horizontaldeformation of the retaining piles, the axial force of steel support and the ground settlementaround the pit. The results show that displacement of pile especially the top horizontaldisplacement of the pile can be used as an important indicator to evaluate the retainingstructure security situation. while the steel support significantly limiting deformation. Thegroud not far away deep excavation will be induced sedimentation tank in the course ofexcavation.Monitoring results indicate that the design program of retaining structure isbasically rational and monitoring program is feasible, which ensure the stability of the pit inthe construction process.(4) By the use of the software FLAC, a simulation of the entire process of excavation isaccomplished.The calculation resulate shuows that the deformation becomes largeraccompanying by the deth of deep excavation.While this change will be stable afterexcavation fishing,which was similar to site deformation laws. It’s results indicate that thedesign program of Monitoring is basically rational and monitoring program is feasible.FLAC3Dnumerical simulation coud be used to provide reference to the design ofpre-excavation retaining structure and the formulation of monitoring programs to providereference.