Experimental investigation on the seepage property of saturated broken red sandstone of continuous gradation

The statues of seepage in broken red sandstone may become unsteady due to the effects of water erosion, so it is important to consider the effect of mass loss on the permeability of broken red sandstone. In this study, the seepage property and water outburst were measured through a self-made variable mass seepage experimental system. In the test, the particles of broken red sandstone satisfied the Talbol grading theory. The influences of Talbol index n on the hydraulic, mass loss of particles, porosity and permeability were investigated. The experimental results show that the seepage process in the broken red sandstone usually experiences three stages: the initial stage, mutation stage and stabilization stage. Broken specimens can bear water erosion at the initial stage. However, the internal structure of specimens produces instability because the seepage of small particles gradually increases in the mutation stage. Finally, stable underground watercourses of the specimen were formed at the stabilization stage. It is also found that the mass loss, the peak of mass loss rate, the final porosity after seepage, the permeability at the mutation and stable stages were negatively related to the Talbol index n of the specimen. The seepage mutation occurred sooner for smaller n. The permeabilities of specimens with different Talbol indices differed by more than 10 times after seepage mutation.