A Review Of Alluvial Overburden Stripping Methods ? Introduction

With modern exploration techniques, it seems likely that an increasing number of the orebodies to be found in the future will be under alluvial fans or valley fill. As a result, a larger proportion of open pit mines will be confronted with the necessity for removal of substantial quantities of alluvial overburden; whereas in the past, for the most part, the open pit mine operator has dealt mainly with hard rock. If this proves to be the case, methods, equipment, and costs for alluvium stripping will become an increasingly important factor in open pit mine planning. Several operations are now faced with this situation, and various methods and equipment are used. At Pima Mining Company's operation the stripping ratio is in the range of 6/1 Well over half of the stripping volume is alluvium. The alluvium is removed almost entirely by carryalls hauling direct to a waste dump. Some removal has been accomplished by shovel and truck operation; more will be done by this means in the future. At American Smelting and Refining Company's neighboring .Mission Mine, nearly all alluvium removal is by large shovels and, trucks. U. S. Borax's Boron operation is accomplishing alluvium removal with carryalls but has been investigating other methods and equipment. The various operations in the Gas Hills Uranium District in Wyoming are stripping mainly with carryalls, although some small draglines are employed. The M. A. Hanna Company in the Mesabi Range employs large draglines and conveyor systems for removal of glacial fill. Nchanga Consolidated Copper Mines in Northern Rhodesia strips overburden with a large excavating wheel and conveyor system. There are no doubt other open pit operations with which the writer is not familiar, that are handling large quantities of alluvial overburden.