| With the development of Cutting Hills to Build Cities and Gully Land Reclamation in the loess plateau region,geological disasters induced by engineering interfaces and native geological interfaces have occurred occasionally.As a key part controlling the strength characteristics of soil and rock masses.The existence of interfaces makes the strength deformation characteristics of soil and rock masses significantly different from those of single soil and rock masses.This article selects the contact between loess and mudstone as the research object.Through basic physical tests and mechanical tests,the basic parameters of loess and mudstone were obtained.A certain proportion of loess and mudstone mixture was used as the material of the contact zone,and direct shear tests,uniaxial compression tests,triaxial compression tests,and wave speed tests were carried out on the loess-mudstone combination and the loess-mudstone combination with different thicknesses of contact zone.The mechanical behavior of the combination under shearing and compression was analyzed respectively,and the mechanical effects of the existence of the contact interface and the thickness of the contact zone on this binary heterogeneous structure were explored.Combined with numerical simulation,the mechanism of the effect of the interface effect at the contact surface was investigated.The main conclusion of this article is as follows:(1)The shear strength of the loess-mudstone composite is controlled by the weaker of two adjacent soil or rock masses,and its peak strength exhibits segmented linear variation.At low stress levels,due to the existence of interface confinement effects,the stronger material deforms less and plays a constraining role on the weaker side,enhancing its strength.The shear strength of the composite interface is between the strengths of the two materials.As the stress level increases,the effect of this constraint gradually weakens,and the peak shear strength of the composite interface tends toward the lower limit of the peak shear strengths of the two materials.The envelope of the shear strength of the composite with an interface does not completely follow the traditional Mohr-Coulomb strength criterion,and as the normal stress increases,its peak strength shows a segmented linear variation.(2)The strength and deformation of the loess-mudstone composite are influenced by the coupling effect of contact zone thickness and confining pressure.The peak strength of the compound with a contact surface is between the peak strengths of the two single entities.The peak strength and deformation modulus of the composite decrease with the increase of contact zone thickness,and increase with the increase of confining pressure.Under low confining pressure,the thickening of the thin-layered contact zone increases the bonding force between the loess and mudstone,thus enhancing the strength of the composite.Under high confining pressure,the increase in contact zone thickness further deteriorates the strength of the composite.(3)As a connection link between the two sides of the rock and soil mass,the contact zone of a composite body affects the stress distribution of the materials on both sides when its thickness is relatively thin.This results in changes in the strength and modulus of the materials on either side of the contact zone,leading to different failure modes.However,when the contact zone is relatively thick,the softer contact zone plays a role in dissipating stress,and the overall strength of the composite body is closely related to the properties of the contact zone itself and affects the deformation of the entire composite body. |
