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t • SECTION 4 - HIGH, THICK FILL, MINE BENCH <br /> GENERAL: High, thick fill on a mine bench was constructed either <br /> because of excess material obtained from the excavation of <br /> the bench cut or because of the need to enlarge the <br /> available mine bench space. The fill was probably built by <br /> end-dumping, without any compaction and without foundation <br /> preparation. Fills are thus at an angle close to the angle <br /> of repose. <br /> STABILITY AND OTHER PROBLEMS: Stability of the fills is marginal ; <br /> factors of safety are close to unity. For any analytical <br /> consideration, F.S. = 1.1 should be considered for current <br /> conditions. Tension cracks may indicate potential <br /> stability problems. Erosion, gullying , rilling and <br /> sloughing of the fill surface are common. <br /> RECLAMATION CONCEPT: Flatten the upper portion of the fill to a <br /> slope of 1. 5 : 1 or flatter. Prevent surface water from <br /> areas above fill from entering the fill surface. <br /> . METHOD OF RECLAMATION: Construct a pioneer road at approximate <br /> elevation of the toe of the flattened part of the fill . <br /> From there, push the fill material toward the fill crest. <br /> Alternatively, excavate the fill in slices from the fill <br /> material to construct the buttress at the mine bench cut. • <br /> Grade the surface of the reconstructed fill and round the <br /> crest of it to eliminate sharp changes of the slope. <br /> Establish a vegetation cover on the surface of the <br /> reconstructed fill . Construct diversion ditch along the <br /> crest whenever required . <br /> ANALYTICAL CONSIDERATIONS : Analyze increases of factor of safety <br /> achieved by flattening the slope of the fill . Analyze <br /> potential benefits of including a bench at the toe of <br /> flattened fill portion both for stability and erosion <br /> protection. <br /> PROPOSED LOCATION: # 4 MINE BENCH, NORTH FILL <br /> II <br />