Water saturation effects on mechanical performances and failure characteristics of rock-concrete disc with different interface dip angles

The mechanical performance of rock-concrete interface is greatly affected by water and dip angles in many rock or concrete engineering projects. To investigate the coupled effects of water saturation and dip angle on the mechanical performances and failure characteristics of rock-concrete interface, series of Brazilian splitting tests were carried out on rock-concrete bi-material disc specimens containing a rough interface. During the test, the interface dip angle θ is set to 0°, 15°, 45° and 90°, respectively. A high-speed camera was used to capture the whole failure process, and the displacement field on the specimen surface was also analyzed. The test results show that regardless of dip angle, the peak load of sample decreases after water saturation. The loss percentages of peak load are very close around 20% when the interface dip angles are 0°, 45° and 90°. However, the reduction of peak load is the most dramatic at the 15° dip angle. When the specimen becomes saturated, its stiffness unexpectedly increases at the dip angle of 0° which is followed by a significant drop at 15°, and finally tends to no obvious change. The stress state at the interface of rock-concrete disc under radial compressive load is discussed. The strength weakening degree of rock-concrete disc specimen by water has a very strong correlation with the ratio of shear stress to tensile stress at the interface. The weakening of water on the bearing capacity of rock-concrete structure is the most obvious at θ≈18.43°.