The Study On Compressive Bearing Capacity Of Branch Pile In Sand Based On Particle Image Velocity Technology

Squeezed branch pile is a type of bored pile,which has been widely used in building construction,power transmission tower,transportation,earth-retaining structures,and areas with poor soil conditions.It can withstand the impact of some special geological conditions.The supporting plate is to set the bearing plate in the soil layer with good bearing capacity in different parts of the pile body,and then the friction pile is effectively transformed into multi-fulcrum friction end-bearing pile,thereby changing the force mechanism of the uniform cross-section pile,greatly improve the bearing capacity of the pile,and effectively reduce the settlement deformation.In addition,the branch pile also has the characteristics of effectively reducing the settlement and deformation of the foundation.Due to the limitations of testing methods and the complexity of the pile-soil interaction,the theoretical research on the compression mechanism of branch piles is not mature enough.Therefore,it is necessary for researchers to conduct more in-depth research and put forward more universal theoretical analysis and methods,so as to create greater economic and social benefits for the correct design and application of branch and disk pile foundations.Squeezed branch pile will be affected by the change of the soil displacement around the pile.However,in the process of analyzing the deformation mechanism of the soil around the pile,the traditional method cannot obtain the deformation of the soil around the pile during the compression process of the branch pile.Many related theoretical results have large errors,so this paper designs related test devices and uses more advanced particle image velocimetry to carry out a series of model tests on the compression process of single-branch piles and double-branch piles.By comparing and analyzing a large number of test data of deformation field,the relevant factors affecting bearing capacity characteristics of branch-and-disk pile are determined,the deformation mechanism of soil around the pile is discussed in depth,and the dynamic progressive deformation and failure process of branch-and-disk pile is analyzed.The optimal model of branch-and-disk pile under each control factor is proposed.The main work is as follows:(1)In the process of being subjected to vertical loads,the bearing characteristics of branch piles are affected by many factors.Therefore,this paper uses the method of controlled variables to carry out compressive model tests on the piles with different relative densities,different diameters of branches,different positions of the branches,different distances between the branches and different buried depth ratios.(2)According to the results of the indoor model test of the branch piles under different influencing factors,the load-displacement relationship curve is drawn,and the relative density of the soil,the position of the bearing plate,the diameter of the bearing plate,the spacing of the bearing plate and the depth ratio of the support plate are analyzed.The influence of the compressive bearing capacity of the plate pile,the mechanical characteristics of the soil around the pile under different conditions at different stages are summarized,and the influence of different factors on the bearing characteristics of the branch pile is finally obtained.(3)The change of the soil around the pile during the compression of the branch pile is a complex dynamic process.The displacement vector field and the shear strain field are obtained after the continuous deformation of the soil around the branch pile is calculated by the Strain Master image processing system.Then,through the comparative analysis of the change law of the soil displacement around the branch piles by various influencing factors,the mechanism of deformation and failure of the soil around the branch piles is revealed.Finally,combined with the load and displacement relationship curve,the best bearing performance of the branch piles under different influencing factors is summarized.