Spatial nonuniformity of landslide dam deposition and its quantitative characterization

The strong spatial nonuniformity of dam soil is a key factor for studying the safety and stability of landslide dams. In this paper, a 500 × 500 × 500 mm cubic model box was made, and the dam soil was deposited in it by layered deposition and different sliding angles to investigate the nonuniformity of the deposition. The depositional characteristics and particle size distribution (PSD) variations in different zones of different depositions were analyzed. Furthermore, based on the basic principle of grading entropy, the particle distributions of different depositions using the entropy parameter A−B coordinates were discussed. Finally, an index of nonuniformity Nd was proposed to quantitatively assess the nonuniformity degree of the deposition. We yielded that as the sliding angle increased, the deposition showed prominent sorting characteristics in the sliding direction. The coarser and finer particles were mainly concentrated in the front and back parts of the deposition, respectively. Compared with the traditional characteristic parameters, the grading entropy is more meticulous for characterizing the PSD curve. In the entropy parameter A−B coordinates, the points for the expected uniform deposition are more concentrated, which indicates that the nonuniformity of this deposition is smaller. The points of different zones for the sliding deposition are arch-shaped, and their distribution is more dispersed and directional in these coordinates, which indicates a greater nonuniformity of this deposition. For the sliding deposition, the index of nonuniformity Nd of different depositions tends to increase and then decrease with increasing sliding angle. The Nd of the deposition made by the sliding angle of 60° is the largest at 0.173. However, that of the expected uniform deposition is only 0.057. This study improves the understanding of spatial nonuniformity and aids the disaster prevention and mitigation of landslide dams.