Failure mechanics and design considerations for footwall slopes

CIM Bulletin, Vol. 79, No. 896, 1986

P.M. HAWLEY, D.C. MARTIN Piteau Associates Engineering Ltd. West Vancouver, British Columbia and C.P. ACOTT, Obed Mountain Coal Company Limited Hinton, Alberta

In bedded deposits such as coal or sedimentary iron, economic limits of mineable reserves are clearly defined by the f ootwall of the seams or ore-bearing units. Where open pits are developed in dipping strata, a long, high f ootwall slope may result. In many cases, unbenched slopes excavated along the base of the lowest mineable seam are operationally simple, economically desirable and geotechnically practical, although a variety of failure mechanisms may develop. This paper examines the engineering geology and rock mechanics parameters of importance in the design of footwall slopes. Possible failure mechanisms and stability analysis methods are described. Design considerations for benched and unbenched slopes are discussed with prime consideration given to development of long high slopes without benches or with a minimum number of benches.
Keywords: Rock mechanics, Bedded deposits, Open pit, Footwall slope, Benches, Unbenched slope, Failure mechanisms, Slope stability analyses, Slope design, Geotechnical assessments.