The Experimental Study On Mechanical Properties Of Interface Between Rockfill Material And Rough Concrete Panel

The problem of the interface between the structure and the soil is widely found in various fields of civil engineering and geotechnical engineering.Due to the different mechanical properties of the two objects,the structure with large deformation modulus under the load will restrain the deformation of the soil near it,resulting in changes in its mechanical properties.Along with the development of Chinese infrastructure,interface problems are more likely to exist in the construction of high-rise dams and large-scale infrastructure projects.Due to the limitation of the size of the test instrument,the previous experimental research on the interface mainly focused on the interface formed by the fine-grained soil and the structural surface.The experimental research on the rockfill and the different roughness concrete panels is relatively rare.In this paper,the improved large-scale direct shearing equipment has been used to carry out a series of monotonic and cyclic shear tests between the rockfill and the different roughness concrete slabs.At the same time,we visualize the test images,the main contents are as follows:（1）In view of the problem that the normal displacement measuring system of original direct shearing instrument has insufficient measurement accuracy,four normal displacement sensors are rearranged to make the position more reasonable,and the interface displacement satisfying the accuracy requirement can be measured.（2）A series of monotonic shear and cyclic shear tests under the contact panel of rockfill and different roughness concrete were carried out.The monotonic test results show that with the increase of the relative roughness of the interface,both the shear strength and corresponding shear displacement increases,and the dilatancy characteristics are more obvious.However,the initial shear modulus is less affected by the relative roughness,and at the same time,when the normal stress increases,the influence of the roughness on the mechanical properties of the contact surface becomes smaller.Cyclic shear test results show that the mechanical properties of the contact surfaces along different shear directions are different,and the interface between the concrete slab and the rockfill is anisotropic.The difference between the rough and smooth concrete slab test is that in the rough concrete slab test,it is found that with the increase of the normal stress,the shear stress shear displacement relationship gradually exhibits strain hardening.There are two kinds of morphological changes in the soil near the contact surface,such as particle breakage and density increase.Due to the contact between the rough panel and the soil,the particles break during the shearing process,the soil gradation changes,and the soil after the particle breaks is compacted,and this phenomenon gradually increases with the increase of normal stress,and finally it appears as a phenomenon of strain hardening with the increase of normal stress.（3）The direct shear test results of the interface were analyzed by means of image visualization.The analysis results show that SolidMotion can better identify the movement of soil particles in the straight-cut box window,and it is concluded that the interface is thick in the monotonic shear test of the interface between the rough concrete slab and the rockfill.The conclusion is that the thickness of the soil is about 5-6 times the average particle diameter D₅₀.