The FEM Numerical Simulation Of The Compound Support Structure Of Pre-stress Anchor Rod And Soil-nail Wall

The compound support structure of pre-stress anchor rod and soil-nail wall is a rising new style of foundation pit support structure combining the two kinds support methods. It is estimated on the practice base, and at present, there is no definite theory base and appropriate design method. In this dissertation, according to the practical case of foundation pit support, the feasible design method is concluded.Summing up the currently popular support structures and basing on these, the support structure of pre-stress anchor rod and rib-girder is analyzed emphatically, with the calculation through asp, a kind of finite element software. Through the comparing between this kind of support structure and the conventional ones such as pile anchor and soil-nail wall, the results are: in the same foundation pit, with the support of pre-stress anchor rod, the maximal plane displacement of the pit is 6.49mm, the maximal bending moment of 26.19kN.m is on the carling, and the maximal pullout force of the anchor rod is 205.26kN; the maximal bending moment of the stake supported by only pile anchor is 204.23kN.m and the displacement except the stake can not be calculated. Comparing with the two support materials, the support structure of pre-stress anchor rod and rib-girder can save concrete by 20% and reinforcing steel bar by 40% than that of pile anchor. Comparing with the support structures of pre-stress anchor rod and rib-girder and of soil-nail wall, the former can actively control the deformation and has a good integer property; the latter passively controls and the maximal displacement of the soil-nail is 7mm, with the displacement of the soil mass supported not being been calculated. These show that all kinds of properties of the support structure of pre-stress anchor rod and rib-girder are better than two other conventional ones.Through the analysis of the support structure of pre-stress anchor rod and rib-girder on the aspects of the mechanism, the deformation properties and the function of the vertical and horizontal rib-girder in the support structure, sufficientlythinking over the properties of the soil-nail wall structure, on the base of date materials from practical working on the ground pit such as the bending moment, the axis force, and the deformation, the dissertation tends to provide a appropriated design method.On the base of wide knowledge about the design methods, through comparing, the numerical method is selected to design the support structure of pre-stress anchor rod and rib-girder. In order to resolve the problem the ANSYS, a big scale FEM software, is adopted. In the process, the soil is simplified to ideal elastic-plastic model; the concrete and steel bar is disposed as lineal elastic-plastic model. Then the appropriated unit types of the soil, the concrete and so on are selected, the proper calculation model is estimated, and the practical simulation to the ground pit supported by the compound support structure of pre-stress anchor rod and soil-nail wall is carried out. Through the comparing between the numerical simulation and the practical measuring data, the conclusion can be made that the method of numerical simulation can definitely calculate the stress and the deformation of the ground pit, and easily find out the deficiency in the design, and optimize the design effect.The research work in this dissertation sufficiently shows the organic combination between the theory and the practice. Besides, the design method of ground pit support has been developed, and moreover, been validated by the practice. These above all provide valuable suggestion for the research work in the related fields.