Experimental Study On The Bearing Characteristics Of Push-type Multi-branch Pile

Push-type Muilt-branch pile uses the principle of bionics to push and extrude the overhanging structure on the hole with the oil-pressure pushing device after the pile is made into a hole and then perfusion.It achieves more operational reliability,flexibility,and effectively solves the problem that the bearing capacity of the pile body is reduced by the mud skin at the side of the pile and the sediment at the bottom of the pile in the post-grouting technology.At the same time,there is still a lack of relevant research on the mechanical characteristics of its "overhanging" structure(branch).How the role of branch resistance to play,how to set up branches,how to predict the settlement of piles,has become urgent problems to be solved.For this,based on the model test and theoretical analysis,In this paper,the study of the support pile is carried out,and the theory of its mechanical characteristics is proposed.At the same time,based on the "load transfer method",the resistance load transfer model of the support end is proposed,and the numerical simulation is carried out based on the proposed model.Some useful conclusions were obtained:(1)Design scale model test to explore the force characteristics and the force process of the branches of the push pile.More than 150 groups of tests were conducted by changing the location of branches,number of branches in each layer,pile length,pile group setting and other conditions,and the rules of anti-settlement performance and bearing performance of multiple piles were obtained.(2)Based on the analysis of the test data,the mechanism of resistance force is proposed.The changing process of the reaction force of the bottom support is explained,and the "Disc effect" and the optimal theory of the branch location are put forward,and the changing mechanism of the support resistance,end resistance and side resistance under vertical load and vertical drawing is put forward.The force mechanism of side pile and middle pile under the condition of setting branch is explained.(3)Based on the load transfer method,a nonlinear expression of the resistance and displacement of the abutment in accordance with the mechanical structure and mechanical characteristics of the abutment pile is proposed.Combined with the load transfer function of three-fold line model for pile lateral friction resistance and hyperbolic model for pile tip resistance,a combined calculation method for settlement of piles is established.