Geotechnical Application for the Design and Estimation of Amata-Lekwesi, Nigeria Open Mine

The need for a proper understanding of the subsurface geology of a place and the depositional pattern of what is to be mined is very important in establishing its mining trend especially if such deposits are not exposed at the surface. Eleven borings were made in the quarry pit and around the surrounding berm to depths of 25 meters at a sampling interval of 1.0m into the intrusive rock bodies using Slanzi rotary diamond coring rig. The depth range of the boreholes varies from 15.0 meters to 25.0 meters. Rock/Soil samples obtained from borings were subjected to both visual field examination and laboratory tests/analyses to guide in designing a mine system that is based on the geology, trending pattern and geotechnical properties of the rocks. The intrusive was observed to trend in the east-west orientation. However, north-south trends were also observed at certain sections of the mine/quarry. The values of the plunges of the intrusive were observed to be between 2o and 6o at the northern southern segments. The average thickness of the intrusive bodies varies from 11.20m for the surrounding bench area to 20.00m in the pit. This observed thickness of rock mass covers an area of approximately 81,750 m2, made up of 29,500 m2 for the floor of the quarry and 52,250 m2 for the surrounding bench. The area of the surrounding berm and the pit floor area are  52,250 m2 and 29,500m2 respectively. A total reserve tonnage of 3,874,000 was obtained. Keywords: Geotechnical, Mining design, intrusive body, Slanzi rotary diamond coring rig, Quarry, Trend, Plung