Model Test Of Vertical Static And Dynamic Bearing Characteristics Of Single Pile In Sandy Soil Foundation Considering The Effect Of Pile Side Roughness

Heavy-haul railway transportation is an important symbol of railway modernization.Smooth prefabricated piles,bored cast-in-place piles,threaded piles and bamboo piles are widely used in bridge foundation and foundation reinforcement of heavy-haul railway.Under the action of high axle load and high density train load,the bearing capacity of pile foundation may be weakened and the cumulative deformation and settlement increase.It affects the long-term service performance,maintenance and even operation safety of heavy-haul railway,but the law and mechanism of the influence of train load on pile deformation remain to be studied.Research on bearing deformation characteristics of single pile under static and dynamic loads considering the effect of roughness is rare.Based on this,a single pile model test system was developed in this paper,and a single pile model test was carried out in saturated sandy soil foundation considering the roughness of pile side.The influence law of roughness on the static and dynamic bearing performance of single pile was studied,and the mechanism of bearing weakening was revealed.The main work of this paper is as follows:(1)A single pile model test system under dynamic and static loads is developed,which includes a separated model box;Water supply saturation system;Single pile with precision sensing instrument;Load and test the system.Contour scanner was used to measure the surface morphology of random model roughness test piles,and the roughness index Rn was used to evaluate the roughness of three model piles.(2)Single pile model tests with different roughness under static load were carried out to obtain the load-displacement curve of pile top,the distribution law of pile axial force and lateral friction resistance,the change law of pile tip resistance and load sharing ratio,and to analyze the influence of pile side roughness on the bearing deformation characteristics of single pile under static load.(3)to carry out the dynamic load under the action of different roughness model test of the single pile,pile top displacement time history curves,hysteretic curves of pile axial force,side resistance and end resistance-time relation curve of pile and soil pressure and pore pressure-time curve,analysis of cyclic loading ratio and roughness effect on dynamic load acting on the pile order of super large pile-cap and pile.