Experimental Study On The Influence Of Roughness On Shear Characteristics Of Soil-structure Contact Surface

The problem of contact surface is widely existed in pile foundation engineering,retaining wall engineering,anchor cable support engineering,landslide support and other important engineering.It is of great engineering and economic significance to study the mechanics and deformation of contact surface between soil and different structures,which can solve the practical problems in engineering.In this paper,the red brown clay and sandy soil in Nanchang area are used as test objects,and the hj-1 ring shear instrument is designed and modified,so that the modified ring shear instrument is suitable for contact surface shear test.Four kinds of structural surfaces with different roughness were simulated successfully by using epoxy resin to paste gravel with different size range on the steel ring.Respectively on the palm red clayey soil and sandy soil with different roughness under different normal stress of the structures of ring shear orthogonal experiment,mainly analyzed the roughness and normal stress on the curve shape of contact surface test,shear stress,shear stress ratio,hardening rate,angle of internal friction and cohesion of the influence of the parameters of the reaction interface shear properties,and the constitutive relation of contact surface is analyzed,the following main conclusions.(1)The larger the roughness and normal stress are,the greater the maximum shear stress of the contact surface between the viscous soil and sandy soil and the structure is.(2)The relationship curves between shear stress and shear displacement of the contact surface between clay and structure all show strain softening phenomenon.With the increase of normal stress and roughness,the strain softening trend gradually weakens.The relationship curves between shear stress and shear displacement of the interface between sandy soil and structure are all presented as strain hardening.(3)The peak shear stress ratio,the residual shear stress ratio and the peak shear stress ratio of the contact surface between clay and structure decrease with the increase of the normal stress and the roughness.(4)The hardening rate of the contact surface between clay and structure did not change with the normal stress.With the increase of roughness,the hardening rate of the contact surface between clay and structure increases,and the shear stress-shear displacement curve of the contact surface between clay and structure tends to be strain hardening.(5)The relationship between the peak shear stress,the residual shear stress and the normal stress on the contact surface between the clay and the structure,as well as the relationship between the peak shear stress and the normal stress on the contact surface between the sandy soil and the structure conforms to the molar coulomb strength criterion.With the increase of the roughness,the internal friction angle and residual friction angle of the contact surface between the clay and the structure remain basically unchanged,while the cohesion and generalized cohesion increase.The cohesion of the contact surface between the sandy soil and the structure is basically unchanged with the increase of the roughness,and the internal friction angle increases significantly with the increase of the roughness.(6)The nonlinear elastic-plastic hyperbolic constitutive model is applicable to the strain hardening curve.The hump softening constitutive model is suitable for strain softening and strain hardening curves,but it can’t reflect the strain softening law of contact surface.In this paper,a piecewise constitutive model based on the damage random distribution theory can better reflect the strain softening law of contact surface,but it has many parameters and is piecewise function.