Experimental study of the shear behavior of concrete-rock interfaces under static and dynamic loading in the context of low confinement stress

Modified static and dynamic shear tests are introduced to study the shear behavior of concrete-rock interfaces under static and dynamic loading in the context of low confinement stresses. Static and dynamic shear tests of concrete-sandstone and concrete-granite interfaces are performed using these techniques. Three levels of interface roughness are considered: smooth, bush-hammered, and rough rock surfaces. The results of these tests show that in both static and dynamic regimes, the shear evolution of concrete-rock interfaces can be described according to three successive stages: the shear stress accumulation, the shear slip, and the residual shear stress stage. The main parameters driving the shear process are the concrete-rock bonds, the interface roughness, and the residual friction. However, unlike in the static shear evolution, in the dynamic shear evolution, the concreterock bonds and the roughness seem active in the shear stress accumulation stage. Furthermore, the correlation between the shear strength and the normal stress is stronger in static than dynamic conditions. The significance of the normal stress on the dynamic shear strength appears more important in rough concrete-granite interfaces than in the other two interfaces. Lastly, the dynamic peak shear strengths of all the interfaces tested are three to four times higher than their static counterparts.