Some Mining Application of Unsaturated Soil Mechanics

Professor David Williams, The University of Queensland

Unsaturated soil mechanics continues to play poor relation to saturated soil mechanics, in part because of the dominance of conventional soil mechanics approaches involving saturated conditions, perhaps because the inclusion of another phase (air) adds considerable complexity, and because a soil at a given density is stronger, less compressible and less permeable (i.e. performs better) than the same soil in a saturated state. However, there are many applications that are unsaturated, not least in the mining field. Mining examples of unsaturated conditions include the wetting up and drain down of initially dry surface waste rock dumps; the irrigation and drain down of heap leach materials; the drain down, desiccation and rewetting of mine tailings; the dewatering of mineral products such as coal; the strength and compressibility of stored mine wastes; and the performance of geo-covers placed on mine wastes by way of rehabilitation. This seminar highlights the key unsaturated soil mechanics parameters involved, overviews the nature of mining and mineral processing wastes, and some mineral products, and discusses a number of the issues involved. Some applications of unsaturated soil mechanics addressing the strength, compressibility and permeability of mining and mineral processing wastes, and mineral products, are presented, together with data to highlight them.

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