A field study of beaching behaviour and the in-situ moisture regime of tailings during active deposition

This research investigated the in-situ beaching and drying behaviour of platinum tailings in relation to proposed mechanisms described in literature and predicted from laboratory behaviour. Successive field depositions allowed the impact of finer grinds, slurry density and beach length to be investigated and compared to flume tests, indicating beach length to be a key parameter. By monitoring gravimetric water contents following deposition the quantity of water released during sedimentation showed that the beach acts as a natural “machine” thickener. After sedimentation the water content was observed to decrease, at a rate correlated with Reference Evapotranspiration, reaching a steady state condition. Field capacity values determined from laboratory experimentation and numerical modelling correlated closely with this steady state condition; restricting further moisture loss due to the relative abundance of moisture to replenish deficits. Liquidity indices demonstrated that as a result only the head of the beach dries sufficiently to impound the waste

Liquefied Strength Ratio with Stress Densification and Low Stresses

This paper presents a comparison of four (4) assumptions or approaches for using a liquefied shear strength ratio for sandy soils in cases where there has been a large increase in effective vertical stress, e.g., structure raising or remedial measure, that is outside the effective stresses of the case histories used to develop the empirical liquefied shear strength ratio and penetration resistance correlations. Changes in penetration resistance due to an increase in effective vertical stress are used in an example to illustrate the following four (4) assumptions for determining a liquefied shear strength ratio in such a post-liquefaction stability analysis: (1) initial effective vertical stress and initial penetration resistance, (2) initial effective vertical stress and the expected increase in penetration resistance due to the increase in effective vertical stress, (3) final effective vertical stress and initial penetration resistance, which is suggested, and (4) final effective vertical stress and final penetration resistance. This paper also presents suggestions for using a liquefied strength ratio at low effective vertical stresses, e.g., approaching the toe of a dam or embankment, in a post-liquefaction stability analysis.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author