Finite Element Analysis Of Cement-soil Mixing Pile Composite Soil Nailing Support System

Although traditional soil nailing structure is widely used in excavation engineering, while foundation pit have higher request for deformation control or foundation pit located in the coastal soft soil region where water level is higher, this kind of supporting structure is not applicable.for its limitations. Composite soil nailing structure which adopts the advanced supporting measures such as mixing pile arises at the historic moment, the system with its adjust measures to local conditions, flexible combination, and inherit the characteristics of traditional soil nailing, such as short time limiting, low cost, the relative environmental protection, so it breaks through the soil nailing limits, more widely applied in foundation pit in coastal soft soil area. Composite soil nailing is developing rapidly, but still we should strengthen the supporting system in the study of the application of the soft soil, the paper takes the application of soil-cement mixing pile composite soil nailing support system in foundation pit excavation in deep soft soil as the research object, in a excavation engineering as an instance, combining with the finite element analysis software MIDAS/GTS on its deformation and internal force were analyzed, and the main research content is as follows:(1) Elaborate the emergence, development and research status at home and abroad of the soil nailing and composite soil nailing, study of soil-cement mixing pile composite soil nailing support system of the working mechanism and failure mode of each component, calculating stability analysis and points out that considering the shear performance of pile body in the importance of stability checking.(2) Have a short introduction of the basic theory of finite element, the finite element software MIDAS/GTS and constitutive model of soil, with the aid of equivalent flexural rigidity principle, the equivalent thickness formula of mixing pile is derived, and analysis the process of establishing simplified three-dimensional finite element model, a detailed analysis of mixing pile composite soil nailing structure in foundation pit construction process in various deformation characteristics and soil nail stress character; through the establishment of more groups of three dimensional finite element model to investigate soil nailing prestressed size and arrangement, pile embedded in fixed length, pile thickness, the outer diameter of interpolation steel tube in pile, size and location of overload in top slope,all of which will have a impact on deformation to the mixing pile composite soil nailing support system.(3) A foundation pit engineering in foshan with which MIDAS/GTS software is adopted to establish the three-dimensional finite element model is analyzed, the results of simulation analysis compared with monitoring results, verify the applicability and rationality of three-dimensional finite element model; to consider the effect of foundation pit engineering on the surrounding environment,the article explores the foundation pit engineering and after pile lateral surface subsidence prediction method, and an engineering example is adopted to improve the formula, through which the calculated results are compared with the monitoring results and the simulation analysis results to verify its applicability.