The correlation between the pre-consolidation and Instantaneous Yield Locus (IYL) of bulk solids

Abstract

The storage and transportation of bulk materials has seen a continuous increase in demand with the evolution of renewable energy systems and modern society. The extraction of minerals such as iron ore, copper, nickel, bauxite, and lithium is leading to the exploitation of previously abandoned mine sites as well as ore bodies that may have been disregarded. This demand necessitates more efficient systems to transport these bulk commodities from the mine site to the export terminal or end user. The design of new bulk material handling systems typically requires the measurement of the bulk material strength, commonly determined using a Jenike direct shear tester. Initially, these measurements were used for the design of free-flowing bulk commodities, such as grain in storage silos or granaries. Over more recent decades, Jenike direct shear measurements have been used for the determination of the flow properties of problematic bulk materials which show cohesive characteristics. Specifically, this testing is used to define the flow function of a bulk material, the relationship between the material strength and major principle stress, which is subsequently used in the design of material handling systems.This paper provides a mathematical relationship between the pre-consolidation and the Instantaneous Yield Locus (IYL) of a bulk material sample under Jenike direct shear testing conditions. When the voidage between the particles is considered, this relationship becomes critical in defining the stress states of a bulk material sample. By understanding these stress conditions, further insight into the tensile forces which lead to problematic material behaviours can also be gained. This becomes increasingly important when low consolidation applications, such as transfer chutes, are considered as this leads to blockages and therefore downtime and lost revenue within a mining operation results. To further gain an understanding of the tensile forces acting within a bulk material sample, inter-particle adhesion tests are compared with predicted values which are determined using the outlined mathematical relationship.