Improved Design And Numerical Simulation Of Composite Support Structure Of Cement Soil Pile And Soil Nail

In recent years,with the continuous development and perfection of the design theory of foundation pit engineering,the application of the composite retaining structure of cement soil pile and soil nailing is more and more.In deep foundation pit,it has more advantages than ordinary soil nail retaining structure in water sealing,impermeability and advanced support.Therefore,it has better economic effect and broad application prospects.However,in theory,there is still a lack of correct understanding of the working mechanism and stability of the composite retaining structure of cement soil pile and soil nailing,which hinders its practical application.In the theoretical research,only the cement soil pile is considered as the safety reserve,instead of taking into account the sharing effect of the cement soil pile on the earth pressure,those are the current design ideas.However,there are some problems in the selection of the calculation model.The cement soil pile in the whole working conditions is regarded as a cantilever beam model,but in practice,soil nailing begins to bear earth pressure after the second working conditions.This paper considers that the cement soil pile from the second working conditions and their later conditions should be regarded as statically indeterminate beams fixed at one end and fixed hinged at one end.Based on this,the formula of bearing capacity of cement soil pile is deduced and improved.This paper uses the finite element theory to build the finite element ABAQUS model of the composite retaining structure of cement soil pile and soil nailing,and analyzes the simulation results based on this model.The model mentioned above is used to study the force and displacement of cement soil pile,the displacement of foundation pit slope and the distribution form of soil nail axial force during the construction process of excavation foundation pit.The feasibility of the improved load sharing method is verified by an engineering example,which provides a reference for similar projects.