Lawrence Charlebois - Geological Engineer - Robertson GeoConsultants

Beaches have a way of attracting attention. Hoards of curvy North Americans flock each year to ocean-side resorts just to sit in pools and stare at beaches. Tailings engineers are no less immune to the draw of beaches, though you won’t find many tailings engineers modeling the latest swimwear on sub-tropical shores (if I am wrong here, I do apologize, and please send us your latest vacation photos).

Beaches have a different meaning to folks on a mine. Beaches at mines are made with tailings, tailings are made from rock, and rock is where we find the ore. Miners are really just speeding up the geologic clock, converting competent rock into grains to be deposited on beaches – their tools are precision explosives, electric shovels, ball mills, positive displacement pumps, and pipelines. Nature uses wind, rain, and gravity to build her beaches from mountains and does an exquisite job, too.

Many have studied beaches, both natural and miner-made; not surprisingly, the two are very similar. No matter the origin of the material, Nature has a way of sorting things out in a chaotic, random, yet geometrically similar way. Melent’ev, Blight, McPhail, Fourie, Williams, Küpper, Fitton, and Simms are the more common names associated with tailings and hydraulic fill beach research. Vladimir Melent’ev in 1973 looked at the formation of beaches resulting from the placement of hydraulic fill and in 1991, Angela Küpper examined the beaching behaviour of oil sands tailings in northern Alberta. All have contributed much to the science of beaches and have left us with many new questions to explore.

You may be interested to know that most all beaches are not flat, sloped ramps but rather gently curving surfaces, the kind you would trace with a draftsman’s French curve. This fact has implications for tailings management, but is not often acknowledged in practice. There are many mathematical equations used to describe beach shapes, some very simple and some with more statistics and thermodynamics than most can stomach.

Miners have tried hard to build beaches that suit our purposes – upstream beaches as embankments, beaches for seepage control in tailings ponds, and beaches that ensure the optimum density of material within a given footprint. Many beach designs are successful, but many more are ongoing processes of trial-and-error, requiring adjustment of valves and pressures, feed rates, and dilution water to get the beaches looking just right. Wiser engineers than I would call this the Observational Method approach, and I would agree it is an invaluable tool for mine operators. The thermodynamics and statistics are best left with academics and consultants with big budgets.