Cement Mixing Pile Composite Soil Nailing To The Pit Supporting Applied Research

Excavation retaining technology is a hot topic in geotechnical engineering. Conventional soil nailing has its own limitations, limiting the scope of its usage, so emerged the composite soil nailing. Cement mixed pile composite soil nailing is a common method in which cement mixed piles are used as membrane barrier curtains, with advantages such as short construction length, low cost, little influence on the environment. This method has been widely applied in coastal areas where underground water level is high and the soil is relatively soft. But the research on this method is relatively backward, which means further efforts are needed to improve the theory and method for its designing and calculating. Based on a foundation pit project, using ABAQUS software, this paper analyzes the deformation and internal forces of cement mixed pile composite soil nailing. The main work and research contents of the paper are as follows:(1) This paper elaborates the formation, development and research status quo of soil nailing technology and composite soil nailing technology, and clearly illustrates the definition of composite soil nailing. Comprehensive analysis of the working mechanism of cement mixed pile composite soil nailing, and investigates the methods of checking computations for the stability of cement mixed pile composite soil nailing.(2) Combined with the project, this paper analyzed the deformation behavior of cement mixed pile composite soil nailing by field testing. Reached conclusion that the horizontal displacement of foundation pit increases during the construction process. Duration and soil consolidation have greater impact on surface sedimentation. The maximum horizontal displacement has a linear relationship with the depth of excavation. normal distribution probability density function is used to check the surface sedimentation, and getting the better prediction results.(3) Simulated the composite soil nailing with finite element method by ABAQUS software. this paper Analyzes the rules of deformation and internal force of composite soil nailing. The results show that the finite element method can simulate the field performance fairly well. The maximum horizontal displacement of the mixed pile is in the middle lower part of the foundation pit, while the maximum of the sedimentation is about the same as the depth of the excavation behind the mixed pile. For the cement mixed pile composite soil nailing, the axial force in soil nails almost decreases along the length of the nail, with the maximum appearing on the connecting point between Cement mixed pile and nail.