Based On Deformation Control Of Composite Soil Nailing Wall With Steel Micro-pile Finite Element Analysis Method And Application

Composite soil nail wall have the advantages of safe, reliable, and convenient construction, as well as low cost. It is widely used in the foundation pit engineering. Nevertheless, theoretical study on composite soil nail wall technology lags far behind in engineering practice, and there are still many problems to be solved in the design. To date, the research on the deformation control of micro pile composite soil nailing wall is relatively few. It is of practical significance to study the deformation of the composite soil nailing wall with micro pile.Based on the investigation, this paper summarizes and analyzes the results of the research on the composite soil nailing wall of steel pipe micro pile, and expounds the deformation mechanism of micro pile composite soil nailing wall, and the problems existing in the research stage. Numerical simulation is carried out using the software MIDAS / GTS, study of steel micro pile composite soil nailed wall support foundation pit deformation and tube micro pile spacing, diameter, embedded the influence of embedded depth of foundation pit deformation, combined with the actual project monitoring data validate the modeling method and the model is correct, and carries on the optimization of project case, for the similar foundation pit engineering design and construction for reference. Through theoretical analysis and engineering case and numerical simulation to obtain the following main results:(1)Micro steel pipe pile and composite soil nailing wall foundation pit excavation modeling, soil hole length can choose 3~5 times of the excavation depth, the pit bottom soil depth can choose 2 to 4 times of the excavation depth; soil nail and anchor bolt should adopt the bar element, micro steel pipe pile are advised to use beam element, is conducive to analyzing the law of deformation and reduce the amount of computation.(2) Steel tube micro pile can effectively control the deformation of foundation pit. In this paper, using MIDAS/GTS numerical simulation, in a single soft soil layer in the steel pipe of the micro pile is no more than the micro pile support, the top horizontal displacement and the maximum surface settlement is reduced by about 10%~15%.(3)Tension above the outside pit excavation; with the excavation of foundation pit, micro steel pipe pile bending moment value increases; below the bottom have obvious positive and negative bending moment value changes.(4)In the design of micro pile composite soil nailing wall, the reasonable spacing, diameter and embedded depth can be controlled effectively, and the cost can be controlled.