Effect Of Excavation Sequence On The Deformation Of Composite Soil Nailing Wall By DEM Simulations

Composite soil nailing wall has the advantages of safety, site adaptability, low noise, low construction cost, short construction period etc.. In recent years, it has been widely used in deep excavation engineering, and achieved good economic benefit and social benefit. However, the current design of composite soil nailing wall is the main reference is the traditional soil nailing design and experience, theoretical research is still not perfect, research on its mechanism still needs further attentions. By using the PFC3d software and discrete element method simulation? the two kinds of composite soil nailing wall excavation sequence of deformation characteristics are compared. The two excavation orders are:1, from the edge of the excavation to the middle of the excavated site(bian-xiang-zhong for short)2, from the middle of the excavated site to the edge of the excavation(zhong-xiang-bian for short). To provide reference for the design and construction of composite soil nailing wall, the main research contents are as follows:1, Using particle flow software PFC3D, through the analysis of the physical parameters of soil nailing, minisized pile and shotcrete face layer, a3D model of composite soil nailing wall in pit excavation was reasonably established, which could provide reference for future research.2, By taking use of particle flow software PFC3D, the two kinds of excavation sequence were simulated to study and compare the deformations of composite soil nailing wall in each layer excavation. The micro parameters evolution during excavation were also in comparison.3, By comparing the deformation and microscopic parameters of two kinds of excavation sequence, it is found that the deformation of the composite nailing wall in zhong-xiang-bian sequence is smaller than that in the bian-xiang-zhong sequence. At the same time, through the analysis of mechanism at the micro scale, the sensitive areas of deformation were studied for two different sequences in each layer excavation in order to provide recommendations for engineering design and construction. 4, By changing the construction parameters, including nails’stiffness, minisized pile stiffness, and speed of excavation, the effects of two different excavation sequences were compared. The results show that to increase soil nail’s stiffness and to speed excavation up can effectively limit the deformation of foundation pit, The zhong-xiang-bian sequence always has a smaller influence on pit deformation than the bian-xiang-zhong sequence.