To study the influences of roughness

gravel content

and normal stress on the shear mechanical properties of the interface between limestone spoil mixture and concrete

a series of interface shear tests were carried out on limestone spoil mixtures with four types of gravel content and concrete surfaces with five types of roughness under different normal stress conditions by using a new large-scale direct shear apparatus. The influences of roughness

gravel content

and normal stress on the shear strength of the interface were investigated

and the internal relationships between roughness

gravel content

normal stress

and the shear mechanical properties of the interface

as well as the mechanism of shear strength were revealed. Test results show that under the same normal stress condition

as the roughness increased

the shear strength of the interface increased and then decreased

and the rough interface significantly increased the degree of dilation of the interface

but with the increase in normal stress

the influence of roughness on the shear strength and normal deformation of the interface was weakened. Under the condition of same normal stress

with the increase in gravel content

the variation of the shear strength of the interface was closely related to the magnitude of the normal stress. Besides

the shear strength of the interface was highly consistent with the Mohr-Coulomb strength criterion

and the influence of roughness and gravel content on the apparent cohesion of the interface was more significant than that on the internal friction angle of the interface. To a great extent

rational roughness and gravel content can improve the shear strength of the interface between spoil mixture and concrete.