Pressures on the support columns buried in iron ore stockpiles

• Experiments with iron ore by tactile sensors verify and update Roberts' approach.
• Passive stress state or a combination occurs at front face for loading and storage.
• An active stress state occurs near the rear face during loading and storage.
• An active stress state occurs both at front and rear faces after discharge.
• The pressure increase due to load settlement during storage is significant.

This paper presents the results of experimental investigations aimed at the determination of the loads exerted on support structures buried in gravity reclaim stockpiles. Structures, such as trestle legs to support load-out conveyors in open stockpiles, or columns to support roof structures and load-out conveyors of enclosed bulk solids storage sheds are subject to the loads exerted by the surrounding bulk solids. The complexity of these loads has been discussed recently (Roberts, 2007 [1], Katterfeld and Roberts, 2009 [2]). According to the theoretical approach proposed by Roberts, both active and passive stress states in bulk solids contribute considerably to the pressure distributions on these support columns. The findings of the preliminary experimental studies carried out by Roberts match with the theoretical predictions. However, follow-up work is required to further validate and improve the design equations for the determination of the loads on support columns. Based on Roberts' prediction model, a laboratory scale test rig was constructed to measure the loads on both the front and rear faces of a buried column. Tekscan tactile pressure sensors were employed in the pressure measurements. Stockpile tests under three different conditions were investigated, and the measured results correlate well with theoretical predictions from modified Roberts' theory. The outcome confirms that Roberts' theory can contribute to the design criterion regarding the loads on buried structures in stockpiles.

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