Assessing the capacity of dredging excavations to place dredging tailings dumps in the course of deep and man-made placer mining

Abstract

Introduction. The dredge stern is often backed up by dredging tailings in the course of deep and man-made placers dredging. One of the reasons for that is the decreased capacity of dredging excavations at the dumping point caused by collapsed pit walls, which is not taken into account by known design methods. Research objective is to evaluate the degree of the developed space capacity reduction at dredging pits for dredging tailings storage, depending on the dredging conditions. Methods of research. Capacity prediction for a dredging excavation for dredging tailings storage should consider natural slope formation of open pit walls during the period of dredge advance to a distance equal to the distance of the poop decks from the face. The degree of reduction in dredging excavation lower part receiving capacity should be set based on pit walls flattening, which depends on rock composition (cohesiveness degree), loose deposits thickness, face width, and dredge working parameters. Results. The results of graphic-analytical calculation revealed that dredging excavation lower part receiving capacity is reduced from 3 to 10% due to pit walls collapse as loose deposits thickness increases from 10 to 34 m for the most favorable face width of a 380-liter dredge, which may result in a significant increase in dredge stern backing up by dredging tailings. Conclusions. At deep and man-made placers, when calculating the parameters of a dredging tailings dump, it is recommended to introduce an amendment into the existing methods, that considers the developed space lower part capacity reduction due to pit walls collapse.