PFC Numerical Analysis On The Composite Soil-Nailing In Sandy Gravel Layer At A Project

Development and utilization of underground space is an important part of urban construction, which increase the number of foundation pit.Composite soil-nailed wall is of highly security, short construction period, highly economy, wide range of applications and other advantage. Thus it has been widely used in Foundation pit support. However, because of its complexity structure, there is a little theoretical study which leads to we are not clear about its working mechanism..This article tries to analyze its inner working mechanism with A two-dimensional particle flow model of soil nails support foundation pit that is established and excavated by PFC2 D, which is based on discrete element method(DEM). This article also tries to provide reference for the design and construction of composite soil-nailed wall. The main work of this article can be summarized as follows:(1)Carry on numerical simulation research and summarize the whole destruction process of thefoundation pit slope and support mechanism of soil-nailed wall. Soil-nailed wall improve the stability of the foundation pit, which helps the unstable foundation pit without support reaches a steady state.(2)Calibrate the microscopic parameters to be used in the actual engineering simulation, using the macro parameters in engineering investigation report with biaxial test to calibrate parameters.(3)Study the support mechanism of soil-nailed wall in sandy gravel layer. Since the particularity of the mechanical properties of sandy gravel layer, support mechanism of soil-nailed wall in sandy gravel layer needs further study. Study the relationship between the effect of soil-nailed wall and different length, dip angle and separation distance of soil nailing. The results show that there is a critical length of soil nail and it also has the optimal angle of dip. The smaller the separation distance of the soil nails is, the stronger the constraint on the top of the foundation pit is, this makes the deformation smaller and becomes more stable.(4)Study the support mechanism of composite soil-nailed wall in sandy gravel layer, and make a particle flow model of a project’s deep foundation pit in sandy gravel layer. During the process of excavation and support, research the deformation and stress of the composite soil-nailed system, and compare it with the actual detection curve.