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Model study of sloped tailings deposits

University of British Columbia

Present tailings disposal methods are subject to limitations that warrent the development of alternative disposal techniques. A recently proposed method is the thickened discharge disposal method, which involves sloping tailings towards a downstream embankment, thereby reducing the height of the embankment required to store a given volume of waste material. The seismic stability of such slopes is a concern and model studies were performed to investigate their stability. The model was composed of a sloped deposit of fine sand 81 cm long, 20 cm wide and a downstream barrier 14 cm high. Slopes ranging from 4 to 14 percent were subjected to base accelerations ranging from .025 g to .10 g. Test deposits subjected to accelerations above a critical acceleration, dependent on the slope angle, were observed to liquefy and flow. These test deposits came to rest at a final slope of approximately one percent. Model deformations were recorded and liquefied deposits were observed to behave similarly to a viscous fluid. A viscous fluid model was found to predict actual partical displacements reasonably well. Although application of test results may be limited to size effects, it seems appropriate to analyze liquified cohesionless material as a viscous fluid. It is suggested that a statically stable sloped tailings deposit, upon liquefaction to a significant depth, may become unstable. The resulting flow, governed by post-liquefaction mechanical properties, could overtop a downstream embankment.

Text

2010-04-22

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http://hdl.handle.net/2429/24097

Civil Engineering

University of British Columbia

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