Nonlinear analysis of load transfer of grouting branch-type anchor

Based on the indoor model pull-out tests on the branch-type anchor, the variation characteristics of the load-displacement curve and the axial force transmission characteristics are studied. Then, the mechanical model for the anchor is discussed, and the theoretical formula for the end resistance of disc is derived. Combined with the hyperbolic nonlinear model for the anchor-soil interface, the load transfer model is established by using the sectional deformation coordinated iterative algorithm. Finally, the sensitivity analysis of the parameters such as the ultimate pressure of cavity expansion distribution and the squeezing angle of the branch disc is performed. The results show that the load displacement curve can be divided into three stages. The axial force distribution decreases along the anchor depth and the step mutation occurs at the branch disc, and the load ratio also increases continuously. The calculated results are basically consistent with the indoor measured data, which verifies the validity of the model. The ultimate pressure of cavity expansion increases rapidly and nonlinearly along the radial direction of the branch disc and then decreases slowly. The peak value increases with the displacement and moves radially outward with the center of the branch disc as the circular point. The overall distribution changes from "cone platform" to "cylinder". When the squeezing angle is greater than 50°, the ultimate drawing force significantly increases. The research results are of important theoretical and practical significance for the analysis and design of the force of the branch-type anchor.