Experimental study on mechanical properties and brittleness of sandstone-concrete combined body under triaxial seepage-stress coupling

Rock-concrete combined structures are commonly used for reinforcement and anti-permeability in water conservancy and underground engineering construction. Seepage-stress coupling experiments were conducted on sandstone-concrete combined specimens with varying contact surface inclination angles in this study in order to investigate the mechanical properties and failure modes of combined bodies. The results indicate that the contact surface inclination angle significantly affects the strength, brittleness characteristics, deformation, and failure modes of the sandstone-concrete combined bodies. As the inclination angle increases, the strength and peak strain curves of the combined bodies exhibit an N-shaped pattern, while the brittleness characteristics display an inverted N-shaped trend. When the inclination angle ranges from 0 degrees to 60 degrees, the failure mode transitions from overall shear failure to slip failure along the contact surface. Conversely, as the inclination angle approaches 90 degrees, the specimens revert to overall shear failure. Increasing confining pressure and decreasing seepage water pressure enhance the deformation and failure resistance of the combined body, and also reduces its brittleness. These findings offer valuable insights for monitoring and controlling the stability of rock-concrete combined bodies in engineering applications under seepage-stress coupling conditions.