Research On The Soil Pressure Calculation Method To Think Of The Nonlinear Effect Of Displacement In Deep Foundation Pit

During the process of excavation, the magnitude of soil stress decreases with the increase of the displacement on the base of the still earth pressure, and the earth pressure distribution varies from the triangular distribution of the still earth pressure to other distribution with the displacement of the timbering structure. Analysis method of soil-structure interaction is put forward and relevant soil pressure model is established for soil pressure calculation and distribution problem which is ubiquitous in the deep excavation.The thesis introduces the theoretical investigation status of the timbering engineering. Simultaneously, the thesis discusses the calculation theory and analysis method for beam on elastic foundation, and gives an in-depth discussion on earth calculation models of beam on elastic foundation, including elastic theory model and Wenker theory model. The deficiency of elastic foundation finite element method of deep excavation timbering system presently is pointed out via the detailed investigation to the elastic foundation finite element method calculation theory and implement process based on Wenker theory method model. Based on energy theory, The thesis using Timoshenko beam element with three-points, thinking of the earth displacement energy and the timbering structure's shearing displacement energy, builds up the element stiffness matrix with the smallest potential energy theory. Based on the theory of the pile-soil consistent deformation, the principium of calculation method of retaining structure in deep foundation pit is fully explained. The thesis introduces the bedding coefficient in the horizontal direction varying with the soil displacement from soil-structure interaction mode, which makes the timbering structure upwards can be calculated using elastic foundation finite element method as the timbering structure under excavation surface. Then the calculation method is summarized combing the model and elastic foundation finite element method. And TPX program is written using Fortran Power Station to calculate internal force and deformation of the timbering structure.A finite element program considering the influence of deformation, top beam andbrace on retaining structure is designed. Then an approach that can consider theintegrated effects of top beam and brace is presented. Multi-braced retaining structure have been widely used in the deep excavation with consideration of the effects of staged excavation upon the bracing and internal force as well as displacement. A deep foundation pit engineering in Guangzhou is adopted as an example. Correctness and suitability are proved by the comparisons between the calculated and observed results through practical foundation pit project. Based on finite element method, the factors of design, construction and nature environment on effect of internal force and deformation for a retaining structure are studied in detail through the example. Those factors include the insertion depth and stiffness of the retaining structure, the brace position, the prestress and rigidity of the brace etc. Some useful conclusions are obtained.