Numerical Analysis With FEM Of The Deep Foundation Excavation

In this paper, the present status of development and research on the deep foundation excavation engineering is analyzed systemically, and some problems on FEM used in the deep foundation excavation engineering are also analyzed. So based on solving these problems, the stability of the slope and the deformations and the bending moments of the bracing structure of the deep foundation excavation are studied.Generally, the ground that soil and rock stands has consolidated normally by the load of gravity. So in the FEM, the load of gravity should be regarded as initial stress, but in the FEM software, the load of gravity on the model is regarded as exterior load, so the model of FEM induces deformation that should not take place. In order to solve the problem, an amendatory formula is brought forward to remove the deformation by the load of gravity. According to the amendatory formula, the author analyses the change characteristics of the soil stress and strain during excavating, and studies the destroy mechanism of the slope of the deep foundation excavation. The underlying slide surface of the slope is confirmed by FEM. Through c- reduction algorithm by FEM, the stabilization coefficient of the slope is obtained according to different value of c, , the author also compares the result with the circle sliced method and study the difference of the two methods.In the elasticity pole system FEM, the load is taken as the RANKINE earth pressure model commonly, and in the consecutive medium system FEM, the strains of the nodes of the soil are not equal during excavating, which makes the truss of support take place crooked deformation, so these are not according with the excavation engineering practices. In order to simulate better, the method of displacement iteration is brought forward to analyze the deformations and the bending moments of the bracing structure of the deep foundation excavation. Through two examples, the results of numerical simulation agree with the results of measurement, so the effectiveness of the method is verified. By the method of displacement iteration, the factors, such as the embedded depth of piles, the reinforced depth of soil in passive area, the station of support and so on, are discussed, through which much valuable scope of these factors can be obtained and chosen in the deep foundation excavation engineering.