Study On The Stability Of Retaining Structure In "T Shape" Interchang Transition Station Foundation-pit In Loess Area

The study of deep foundation pit of subway interchange stability analysis is one of the key subjects of urban subway construction in the loess areas, and those foundation pit deformation rules have academic significance and economical value to the whole project. This thesis analysis the stability and deformation of retaining structure in "T shape" interchange connection with the foundation pit project of urban subway station xiaozhai in Xian by the method of FEM simulation and in-situ monitoring. The main research results are as follows:(1)The scheme of cast-in-situ bored pile and steel shotcrete combined with chemical churning-pile curtain were choosed by comparing methods. On basis of beam on elastic foundation method, the structure calculation of supporting system was implemented; and the corresponded construction scheme was fixed/determined.(2)According to engineering practice, the feasible monitoring scheme was designed. Based on these, in-suit monitoring job was finished. Focuses on analysis of supporting pile's deformation and supporting axial force's change rules was executed.(3) Relative theory and methods on the simulation of foundation excavation by means of the finite element method(FEM) were researched and analyzed. Combining the project practice, selecting Duncan-Chang model, seting Goodman's interface element between pile and soil, releasing load in excavation by Mana methed, and control value of axial force and pre-axial force were established..(4)Mechanics parameter of soil material was defined on the basis of displacement back analysis and indoor material mechanics tests. The FEM model of dynamic Construction of foundation pit was established. The construction process of foundation pit was studied. The rules of internal force and deformation of Support System were obtained, and were compared with monitored data.(5)Deformation and stress of soil were deduced by numerial simulation of surrounding soil of foundation pit. The results indicate that soil is of elastic with foundation pit construction, i.e. soil is stability.