Effect of rock shear keys on the shear performance of cold joints in rock-filled concrete structures: Experimental and numerical investigation

Rock shear keys have been applied in rock-filled concrete (RFC) cold joints to improve the shear resistance through aggregate interlocking action. However, the failure mechanism of RFC cold joints remains unclear, and the role of rock shear keys has not been quantitatively evaluated. To investigate the effect of rock shear keys, a series of small-scale shear tests of RFC cold joints using experimental and numerical methods were conducted. Various influential factors were considered, including normal pressure, material strength, and the distribution of rock keys. Failure mode, shear capacity, deformation, and their relationship with the influencing factors were analyzed. The results show there are two typical failure modes deriving respectively from self-compacting concrete (SCC) (Mode II) and rocks (Mode I). It's observed the shear capacity is positively correlated with normal pressure, the exposed height, and the number of rock keys. Moreover, the influence of material strength depends on the failure mode. In Mode I, shear capacity increases with the increment of SCC strength. While in Mode II, increasing the rock strength can effectively improve shear capacity. The study of the distribution of rock keys found that when the exposed height is half of the diameter, and the distance is greater than the diameter, rock keys work optimally. Finally, an empirical formula was proposed based on current test results.