Mechanics of bulk solid stockpiles

Despite the capital cost and strategic importance of stockpiles to the materials handling industry there is a lack of information available relevant to the design of stockpiles. The small number of publications is indicative of an incomplete understanding of the underlying mechanics. Of the existing literature, much is concerned with highly idealized modelling of base pressures and limited laboratory measurements thereof. The direct application of this information to industrial design is currently limited. The majority of current stockpile designs are based around empirical models. Reclaim capacity is often predicted assuming a single draw down angle that grossly overestimates the reclaim capacity. Loads experienced by the reclaim tunnels are assumed to be low compared with those measured in the test work. Feeder loads by manufacturers tend to be based on empirical models which have evolved to provide workable solutions that are not necessarily optimised, or transferable, for different bulk material/feeder arrangements. Given this background, research was conducted into a wide variety of areas vital to the successful design of stockpile systems. Substantial improvements in many of the investigated areas have resulted. This thesis details the research with outcomes including: New test methods to evaluate interparticle bonding (caking) during dehydration; This can have significant impact on materials handling plants; Details of a new loadcell, designed for high quality base pressure measurements, ease of manufacture and field applicability; Methodology for CAD prediction of reclaim capacity based on material properties and stress distributions with a stockpile; Refined theory for predicting the initial and running loads experienced by feeders located under gravity reclaim stockpiles; Stockpile base pressure measurements; and, A continuum model of the 'M' pressure effect is presented to aid in the understanding and prediction of stockpile base pressures. Overall, this research has enabled the formation of a complete rationale for the design of both gravity and mechanically reclaimed stockpiles commencing with the fundamental bulk material properties. The development of the stockpile loadcell was pivotal in the research program providing key insights into the stress propagation throughout the pile. These results enabled significant refinements in the reclaim prediction and feeder load theories developed early in this research programme.