Shear Characteristics And Mechanics Of Friction Pile-sand Interface Transfer Model Research

In sandy soil areas,friction piles are usually used to reinforce the foundation.The friction between the side surface of the pile and the foundation soil determines the bearing capacity of the pile,and the working characteristics of the pile-soil interface have a significant impact on the friction.In order to explore the shear mechanical characteristics of the pile-soil interface,the development law of the shear zone,and to solve the coupling problem of force and roughness in the calculation of the interface between sand and concrete,a large-scale visual interface shear test device independently developed by me Photographing and image processing technology,supplemented with ABAQUS finite element software,carry out the direct shear test of pile-sand soil under the influence of different normal stress?50k Pa,75k Pa,100k Pa?and different roughness?0mm,0.393mm,0.720mm?,the result shows:?1?With the increase of normal stress and roughness,the peak value of shear stress,its displacement,and the slope of the elastic stage also show an increasing trend.When the roughness R>0.393mm,the strain softening phenomenon is more obvious.At this time,the shear stress The increase and peak value will increase obviously;under the condition of low normal stress,the proportional limit displacement is less affected by the roughness,and the limit shear displacement is greatly affected by the roughness;under the high normal stress condition,the proportional limit displacement is affected by the roughness Larger,the ultimate shear displacement is less affected by roughness,and roughness has less effect on the residual strength critical displacement.Therefore,changing the surface roughness of the pile side within a reasonable range can effectively improve the strength of the contact surface,thereby increasing the ultimate bearing capacity of the pile foundation.?2?The greater the normal stress and roughness,the more obvious the movement of the sand particles in the shear zone,but the low normal stress has less effect on the normal displacement of the contact surface.Under low roughness conditions,the shear expansion rate It is easier to achieve stability.When the roughness R>0.393mm,the increase rate of the normal position and horizontal displacement of the sand particles is significantly higher than that when R?0.393mm;normal stress and roughness are the main factors affecting the thickness of the shear zone.The development rule of the cutting zone is significantly affected by the cutting direction.?3?The relationship curve of shear stress-shear displacement conforms to the rule of hyperbolic model,and the expression parameters K_si,?_uand?_nare linearly related.After considering the effect of roughness R on the model parameters,it is proposed that different normals can be achieved Calculation model of mechanical transfer of sand-concrete interface with stress and different roughness coupling.?4?The ABAQUS simulation results show that the stress and displacement at each location inside the sand increase with the increase of roughness,and when the shear displacement is greater than 5mm,the stress and displacement changes at each location inside the sand significantly weaken;As the shear advances,an uneven shear slip zone is generated near the contact surface,where the sand particles move in a larger amplitude,and the thickness of the shear slip zone increases as the roughness increases.The thesis analyzes the influence level of roughness on the ratio strength,shear strength and residual strength of the pile-soil contact surface during the shearing process,and judges the damage law of the pile-soil system,which is combined with the actual project side pile compression,which can be the lowest prefabricated.The economic cost and the optimal bearing capacity of the pile foundation provide a theoretical basis;the modified hyperbolic empirical equation proposed in the paper can simplify the complex load transfer process of the structure surface with different roughness,and then provide theoretical guidance for the calculation of the mechanical transfer of the contact surface;at the same time,The study of the development law of the shear zone can provide a guidance method for judging the deformation trend and damage range of the foundation soil when the pile foundation is under load.The paper has 66 pictures,9 tables,and 91 references.