A Study On The Law Of Site And Excavation Support Conditions On Vertical Shaft Deformation Near The River

With the continuous development of the urbanization process,the urban waterlogging have become the key problems to be solved by the government in China.In addition,the high population density makes the overflow pollution in the urban rainy season area more and more serious.GuangZhou refers to the developed city overseas,to solve the water pollution and water safety problems through the construction of deep drainage system,and selects the donghaochong basin as a pilot.The site conditions of DongHaoChong test section is very complex.It has brought great difficulties to the construction of the deep tunnel drainage system.The depth of excavation of shaft is near 43 meters and the distance from the Pearl River is less than 20 meters,so the ground water is rich in the construction site.The excavation of a shaft should be worn through the floor of the existing pumping station,and there is a 5 meters sand layer at the bottom of the pump station,which is very difficult for construction.The construction support conditions adopted in the original construction plan are relatively simple,so the deformation of the shaft wall are serious in the early stage of the excavation.If continued excavation will cause collapse,and it will even affect the safety of the surrounding buildings.Therefore,the deformation of shaft is studied under the current site conditions,the construction scheme suitable for the vertical well is found,the safety problem of the shaft excavation is solved,and the reference is provided for the future construction scheme similar to the vertical shaft near the river.This paper is based on Donghaochong deep tunnel drainage system of a shaft excavation engineering,uses finite element software MIDAS/GTS to establish the numerical model to verify excavation scheme of the supporting effect,and to study the different venues andsupporting conditions of shaft deformation on the basis of the existing calculation model.The research contents and some important conclusions are as follows:(1)The paper optimizes the original excavation scheme for reference to the tunnel construction measures,and sets up the finite element model of the original scheme and the optimization scheme respectively.After the above steps are completed,the correctness of the numerical model is verified by the field monitoring data.Finally,compares shaft surface subsidence,heave,shaft displacement,horizontal displacement of soil inside and outside the shaft wall deformation of two schemes to determine the optimal scheme of supporting the sealing effect,and summarizes the specific construction measures.(2)Based on the existing calculation models,analyzes the influence of different site conditions(initial water level,soil elastic modulus and soil permeability coefficient)on the deformation of shaft near the river and summarizes the law of deformation.The research results show that when the initial water level is low,the stiffness of supporting structure can not be fully realized.The improvement of soil modulus has little effect on the deformation of supporting structure,and the permeability coefficient has obvious influence on the horizontal displacement of supporting structure.(3)Analyzes the influence of different support conditions(footage of excavation and pipe roof parameters,grouting reinforcement effect and influence of shaft deformation range)on the deformation of shaft near the river and summarizes the law of deformation.The results show that the diameter is too large and will not have a significant impact on supporting structure and uneconomical;good grouting effect and can significantly reduce the surface subsidence and support structure displacement.