Study On The Earth Pressure Of Silty Soil And The Behaviour Of Retaining Structures For Pit Excavation

With the increment of pit foundation in many buildings and metros, the safety of deep excavation is being paid more attention. The above studies mainly focus on theoretical model and distribution of earth pressure. The relation between lateral pressure coefficient and vertical effective stress in passive region in front of wall is still given less concern. This thesis is carried out against a background of Qiutao Road subway station excavation of Hangzhou No.1 metro. The aim is to get the water pressure and earth pressure and to evaluate the internal force and deformation of retaining structure of subway station excavation in silty sand.Firstly, the linear relation between earth pressure and displacement is assumed in this paper, the distribution of earth pressure suggested in national regulation is modified, the finite element programme Mmethod written by VC++ is emended, which is based on the theory of elastic foundation beam. The Mmethod is applied to analyse the internal force and deformation of retaining structure in normal conditions.Secondly, secant modulus and lateral pressure coefficient is obtained from the GDSLAB which simulates the stress path of soil when excavating. According to the GDSLAB, the relation between lateral pressure coefficient and vertical effective stress is established.The facr that the seepage can reduce the lateral pressure coefficient is expatiated. The Mmethod modified by the relation between lateral pressure coefficient and vertical effective stress is applied to analyse the internal force and deformation of retaining structure when shifting sand.happens.Finally, by using emended program Mmethod, the internal force and deformation of retaining structures of Qiutao Road subway station excavation are analyzed in normal conditions and abnormal conditions. And the general rules of the internal force and deformation of retaining structure of subway station excavation in silty sand are given, which will provide references for the similar engineering.