Influence of particle-size segregation on the impact of dry granular flow

Abstract

Even though dry granular flow can cause well-known impact hazards to retaining structures, studies rarely have been conducted to determine the influence of particle-size segregation on the impact of dry granular flow. Based on the existing experiments concerning the impact of dry granular flow, we calibrated a code of the Discrete Element Method and designed three numerical simulations. Two types of degree of particle-size segregation Ns and Nl were defined to show the extent of particle-size segregation in the depth and flow directions. The results of the simulation indicated that a dry granular flow initiated with different degrees of particle-size segregation (Ns) could develop into very distinctive conditions in terms of the relative positions of different groups of particles in the depth and flow directions. The initial deposition with a higher Ns could make it easier for the coarser particles to be located in the front and top of a dry granular flow, with the finer particles being in the tail and bottom of the flow. In the impact process, the greater the values of Ns and Nl are, the more the coarser particles impact the retaining wall at a higher position at an earlier time during the impact. However, a higher degree of segregation of the particle sizes does not necessarily correspond to a higher impact force and action point. It is more rational to use the change of Ns with respect to its initial value as the index to show the influence of particle-size segregation, and a greater change in Ns corresponds to a higher impact force and a higher action point. The greater change of Ns corresponds to a lower energy dissipation, which is accounted for by the friction among the particles in the flow process, i.e.,less contacts among the particles correspond to the less dissipation of energy, which means that more energy can be converted into impact force.