Mechanical Properties and Particle Breakage of Uniform-Sized Tailings Material

Abstract

Tailings dam disasters are reported almost every year and are triggered by mechanisms, such as overtopping, piping, and others. The failures due to inadequate management cannot be neglected as well. These dams are constructed mostly in a step-by-step construction method that leads to a continuously changing state of vertical loads during construction and may lead to particle breakage and changes in strength. Therefore, a layer of tailings dam today may not be the same tomorrow during the construction phase. To study the effects of different loads on particle breakage and strength, direct shear tests were performed on remolded tailings samples that were separated into different particle sizes. The tests were performed using different normal stresses that ranged from 50 to 500 kPa. The results indicate that finer tailings exhibited slightly more shear resistance than that of coarser tailings irrespective of the deposition method. For normally deposited specimen, the dilatant and contractant behavior in vertical height was observed when the normal effective stress was less than 300 kPa and greater than 300 kPa, respectively. Under the vertical deposition method, the finer tailings showed contractant height behavior when subjected to a normal effective stress of 300 kPa. The friction angle and the cohesion of vertically deposited specimens were slightly higher and slightly lower, respectively, than that of normally deposited ones. The breakage of tailings particles was observed to be proportional to the particle size of the tailings.