Study on macroscopic and microscopic shear mechanical properties of the interface between limestone waste slag and concrete

Résumé fourni par la source

The waste slag of soil and rock mixture produced by tunnel excavation is gradually being applied as a filler in roadbeds and retaining structures, forming a typical interaction problem between waste slag and concrete interface. A large-scale direct shear apparatus carried out a series of tests on the interface between limestone waste slag and concrete slab. The effects of different vertical stresses and surface roughness on the shear mechanical properties were analyzed from a macroscopic perspective. In addition, the microscopic parameters of the interface were analyzed by the discrete element software PFC 2.0 . The results show that the surface roughness of concrete significantly affects the shear stress–shear displacement curves of the interface and the volume change of the sample during the shear process. The rough interface can significantly increase the apparent cohesion, therefore increasing the shear strength of the interface between limestone waste slag and concrete. Notably, the shear strength reaches the maximum when the surface roughness is about 1.59. The grain force chain distribution and the fabric anisotropy variation agree with the variation of macroscopic shear strength. The coordination number can better reflect the vertical deformation law of the interface. More so, the smooth interface shows the characteristic of slip failure, and the shear band is not obvious. On the other hand, the rough interface demonstrates a shear failure pattern that evolves from localized deformation to regional failure. Furthermore, the thickness of shear bands in rough contact surfaces is approximately 6–7 times the average particle size of the slag.

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