On uniaxial compression and Jenike direct shear testings of cohesive iron ore materials

The flow function of an iron ore material governs its flowability characteristics in material handling chains of the resource industry. A uniaxial compression test is able to obtain a flow function more rapidly compared to the Jenike direct shear test, nevertheless, results often exhibit lower rankings using the former method. This study aims to investigate the fundamental stress states within the test specimen that led to this phenomenon, and to introduce a new uniform density specimen preparation method for a uniaxial compression test in order to achieve comparative flow functions as per the Jenike direct shear test. The minimisation of the wall friction effect and the achievement of the critical state when preparing a uniaxial specimen were explicitly discussed. Experimental investigations on flow functions of a suite of Australian iron ore samples were conducted using both the uniform density uniaxial compression test and the Jenike direct shear test. Results from both methods were indicated to be comparable providing the specimen exhibited cohesive flow behaviours. Additionally, a simple compressibility index, based on the bulk density test of iron ore samples, was derived as a threshold to indicate if a uniform density uniaxial compression test can produce flow functions matching the Jenike direct shear test. The outcome of this research enabled a rapid and reliable flow function testing method for cohesive iron ore materials. [Display omitted] •A uniform density sample preparation method ensured critical compaction in uniaxial test specimens is achieved.•Uniform density sample preparation method resulted in improved flow function rankings.•Uniform density uniaxial compression test can produce comparable flow function to Jenike direct shear test.•The confined compressibility can be used to indicate cohesive flow behaviours for iron ore materials.