Large-scale test study on the three-dimensional behavior of the gravel-concrete interface of a CFR dam

The mechanics of the interface between a concrete-face slab and cushion layer gravels plays an essential role in the stability of the concrete face of a concrete-face rockfill (CFR) dam, which is indeed very vital for the overall performance of a CFR dam. Large-scale tests were conducted on the interface between a concrete slab and cushion layer gravels related to a real-scale CFR dam project through specialized test equipment. Such an interface was tested along different intricate shear coupling paths, such as linear and rotational shear coupling paths, to perceive the three-dimensional behavior of such an interface. The mobilized strength of an interface is influenced by the shear path. The interface exhibits significant coupling effect in both orthogonal shear directions due to the application of different three-dimensional shear schemes. Significant coupling occurs between the orthogonal shear directions along the three-dimensional shear paths, which determines the flow direction of the interface under the complicated shear. The interface tends to become stiffer because of the hardening behavior of the gravel caused by the cyclic shear history; the shear path significantly affects the hysteretic stress-displacement response. The interface exhibits significant dilatancy and aeolotropy along different three-dimensional shear paths. The shear path significantly influences the dilatancy of the interface, such as the initial rate of increase and the ultimate value of the irreversible dilatancy.