Over the past 25 years there have been a large number of long runout flowslides from Rocky Mountain coal mine waste dumps. The waste dumps are constructed as end-dumped fills with an angle of repose of 38°. Dump heights range between 100 and 400 m. The dumps are normally founded on mountain slopes that are covered with a thin veneer of granular colluvial and dense stony till materials. Conventional stability analyses carried out for these dumps using friction angles equal to the angle of repose for the waste rock and typical values ranging from 30 to 32° for the foundation materials indicate that many should be stable. The flowslides occur rapidly and display surprisingly long runouts of up to 2 km in some cases. Detailed studies of three of these events indicate that static collapse of saturated or nearly saturated sandy gravel layers within the dumps may be responsible for the initial failure and the generation of high pore pressures which result in high runout mobility.Key words: mine waste dumps, flowslide, static liquefaction, collapse mechanics.

Laboratory and field experiments demonstrate that substantial dewatering occurs when the waste clay from oil sands operations is subjected to one cycle of freeze-thaw. The enhanced permeability resulting from the freezing process causes further dewatering and accompanying strength increases during post-thaw consolidation. The findings presented here were guided by a number of different materials handling scenarios which take advantage of the freeze-thaw process and are driven by the appropriate geotechnical, geochemical, and geothermal input parameters. Different conceptual design scenarios are examined to demonstrate how this process might be feasibly implemented at the commercial scale. Emphasis is placed on the large-scale requirements, sensitivity to input parameters, and the coupling of the continuing applied research with the conceptual materials handling models. The latter point is of generic interest to those involved in mine waste management.Key words: mine wastes, freeze-thaw, volume reduction, disposal, large strain consolidation.

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