Estimation of Reserve – Overburden Ratio of A Proposed Quarry Site Using Resistivity Survey: A Case Study of Ajebo, Near Abeokuta, Southwestern Nigeria
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Date
2011
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Publisher
American-Euroasian Network for Scientific Information
Abstract
The geophysical and geotechnical assessment of the granite deposit at Idi-Osan Ofagada village near
Abeokuta, southwestern Nigeria, have been undertaken and the exploitation suitability of the deposit
established. The area is underlain by the granite gneiss rocks of the Precambrian Basement complex of
southwestern Nigeria. Fourteen Vertical Electrical Soundings (VES) of Schlumberger array were carried out on
the areas covered with overburden to determine their resistivity characteristics, overburden thickness and the
reserve tonnage of the basement rock. The compressive strength and the specific gravity of the rock were
measured to determine its competency and density respectively. The area is gridded into 5 by 6 blocks for more
accurate calculations of the parameter for the estimation of the reserve. The reserve is estimated for elevation
datum of 150m, 160m and 170m. Taking into account the economic implication for the removal of overburden,
a minimum ratio of overburden to basement thickness of 1:1 and a limiting 10m overburden is considered to be
the economically exploitable area. The VES results showed a two to three geoelectric layers; the sandy
weathered layer, clayey layer and the basement. The isopach and geoelectric sections revealed that the
overburden thickness varies from 1.5m to 23.6m with the thickest overburden of 10m and above occurring in the
north-western and south-eastern parts. Geotechnically, the deposit has an average compressive strength of
47.68N/mm2 Young Modulus of 633N/mm2 and specific Gravity of 1.615. The reserve estimates obtained for
170m, 160m and 150m elevation datum are 4.42 x 105, 17.17 x 105 and 37.09 x 105 tons respectively. The
results showed that the exploitation of rock in the area is economically viable most especially at 160 and 150m
datum
Description
Keywords
VES, Reserve Estimation, Specific Gravity, Overburden Thickness