Finite Element Analysis To Deep Excavation Considering Of Soil-Structure Interaction

Deep excavation engineering is part of the civil engineering, whose development is interrelated to the building industry closely. With the large quantities of high-rise buildings, the demand to the deep excavation engineering is higher and higher, i.e. the demand to the stability of deep excavation and displacement control is much higher. Thus, deep excavation engineering deals with not only typical strength and stability problems of soil mechanics but also the deformation problems and the interaction between soil and timbering structure.The thesis introduces particularly the theoretical investigation status of the timbering engineering for deep excavation and analyses both basic calculation process of the bar-system finite element and calculation steps used in the deep excavation timbering structure. Simultaneously, the thesis discusses the calculation theory and analysis method for beam on elastic foundation, and gives an in-depth discussion on each calculation model of beam on elastic foundation, including elastic theory model, Wenker theory model, spring-system connected with flexible line model and double-foundation-bed coefficient model etc. 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 model. Analysis method of soil-structure interaction is put forward and relevant soil pressure model is established for soil pressure calculation and distribution problems which is ubiquitous in the deep excavation calculation. Then the calculation method is summarized combining the model and elastic foundation finite element method. And an applied SJK programme is written using Fortran Power Station to calculate internal force and deformation of the timbering structure. Through investigation to the calculation results on different timbering conditions according to idiographic engineering geology conditions, the thesis discusses on how internal force and deformation is influenced by different depth of the excavation, the rigidity of the timbering structure, the position of the bracing and rigidity of the bracing and educes practical analysis result. And because the excavation is often processed in steps duringthe multi-timbering structure construction, the thesis also analyses briefly to the multi-timbering structure on each working condition during the process of excavation and compares it with the actual measurement combining with the analysis method considering soil-structure and load increment method which is put forward in the thesis.Through the analysis and calculation the conclusion can be made that during the process of the timbering 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. The thesis introduces the bedding coefficient in the horizontal direction varying with the soil displacement from soil-structure interaction mode, therefore calculation can be made to get more rational calculation result using elastic foundation finite element method which is the same to timbering structure both upwards and under excavation surface.