The impact of broken rock angle of repose on truck and shovel capacity and tire life

Abstract

ABSTRACT This article outlines a closed-form solution to calculate truck body volumetric capacity. This solution also provides a means of evaluating broken rock density and swell factor, which may be further extended to determine shovel dipper and excavator bucket fill factor. The key to the analysis is an evaluation of the broken rock angle of repose. The analysis procedure defined in this article alleviates the need for using assumed values in operational planning. Further, the volumetric capacity and broken rock angle of repose and density may then be used to evaluate the load distribution within a truck body. This is critical to understanding the impact on tire loading and performance, which may be evaluated and compared to the tire manufacturer recommended tonne-kilometer-per-hour limit. The results of the analysis proposed here indicate that for the truck body designs investigated, the SAE International body design standard angle of repose assumption of 26.6° (2:1 slope) is much lower than most materials hauled (> 33°). Also, the broken rock density assumption in the same SAE International body design standard at 2.0 t/m3 is often too high, and does not permit the target load distribution of 1/3:2/3 front:rear axle to be achieved, effectively placing greater load on the front tires than the rear tires, adversely affecting front tire performance.