Effect of Parallel Gradations on Crushed Rock-Concrete Interface Behaviors

The response of a soil-structure system subjected to monotonic or cyclic loading is significantly influenced by the mechanical behavior of its interface. In this paper, the friction characteristics of crushed rock-concrete interface and the role of the crushed rock deformability were examined through a series of monotonic and cyclic direct shear tests under the framework of parallel gradation technique. Two parallel gradation curves of the crushed rocks were used. All the tests were carried out in dry condition and with two initial void ratios representing both loose and dense states. Two concrete interfaces of different roughness were used in the interface direct shear tests. The static test results show that parallel gradation technique can be used to characterize the residual shear strength but not the volume change. Moreover, under cyclic loading, it can neither yield the same volume change, nor the same shear strength. The critical state of the soil interfaces was also studied, which shed some light on the mechanism of pile skin friction mobilization and modeling of soil-concrete interface behaviors.