FLAC^3D Simulation And Field Testing Of Deep Excavation Supported By Soil Nail Walls

It is a new kind of support technology that combines of the steel pipe pile, prestressed anchor and soil nailing. It can effectively control the pit's deformation, significantly improve the slope's stability. Currently, the method of combined support is less, field test data is extremely scarce, finite element analysis is mostly considered by plane, which caused limited knowledge of studing characteristics of force and deformation.Based on the field test and three-dimensional simulation of deep foundation engineering of An Lelin, this paper discusses the factors of foundation's stability and deformation, in order to provide reference to similar projects.In this paper, the main contents and results are as follows:(1) Describe the mechanism of combined support. Steel pipe pile's high strength and rigidity play a dual role of early support and retaining; through transfer and diffusion of the stress, anchor and soil nailing together regulate soil deformation. Three closely integrated through the surface layer and soil, share the weight of soil and surface loads, maintain the stability and deformation of foundation.(2) Construction field test. Larger horizontal displacement lies in the top and the lower part of excavating surface, about 10 mm. Significantly raising phenomenon of prestressed anchor is due to water leakage, the final tension value stabilized at between 55 80 kN. Apart from individual soil nail, the force along the length of soil nails showed distribution of " large mid-back and small ends". Tests show that combined support's effect to control foundation stability is obvious.(3) FLAC^3D numerical analysis. Model calculated the maximum horizontal displacement of excavation face was 12.48 mm, which lies in the lower part of the slope; surface subsidence was "spoon" shape distribution, the maximum value within a certain range from the excavation edge. Characteristics of prestressed anchor is that non-bond section is constant basically, axial bond section trended decay. Axial force of soil nails distributed like core. Overall, simulation results of the foundation is consistent with experimental results, indicating that the FLAC^3D numerical analysis method is more reasonable.(4) Foundation's impact factors. Analysis showed that the increase in a certain range of steel pipe pile embedded depth, pile stiffness, pile spacing, excavation step by step, reduce the ground overload, have contributed to reduce the pit deformation, strengthening the foundation stability. The foundation design is reasonable, optimization programs can be 3 rows of bolts and 6 rows of soil nailing, facilitate construction and reduce the project cost.