Computer Modeling of Slope Stability in Mining the Tar Sands of South Western Nigeria
40E
80E
120E
120N
TERTIARY
COMPUTER MODELING OF SLOPE STABILITY IN MINING THE TAR SAND OF DAHOMEY BASIN, SOUTHWESTERN NIGERIA
David Afolayan ALAO and Mopa BASSAGI DEPARTMENT OF GEOLOGY AND MINERAL SCIENCES, UNIVERSITY OF ILORIN P.M.B. 1515, ILORIN, KWARA STATE, NIGERIA
Abstract The need to have stable slopes in open pit mining of the tar sand deposit of the Dahomey Basin, Southwestern Nigeria is emphasized in this study. In the Loda village, Southwestern Nigeria, samples of the lateritic soil and alluvial sand which overlie the tar sand occurrence were subjected to geotechnical tests. Computer simulation of bench face angles was carried out using the SLOPE/W software to determine the bench face angle(s) with the least susceptibility to failure. Slope failure might lead to loss of lives and valuable heavy equipment thus increasing overall expense of running the mine. Geotechnical tests carried out helped to determine the unit weight (g), cohesion (c) and angle of o friction (f) values. For the lateritic soil, g = 25 kN/m3, c = 45 kPa and f = 41 . Also, values of g = 18 3 o kN/m , c = 0 kPa and f = 34 were obtained for the alluvial sand. These values were inputted into the software program to simulate different bench face angles that could be cut into the two lithologic o o units. Factor of safety values were obtained for 10 to 90 bench face angles at 1 metre, 4 metres and greater than 40 metres ground water level, respectively. 10 metre bench width and 6 metre bench height were used while 20 metre bench width and 6 metre bench height were also utilized to make room for heavier equipment. Factor of safety values ranging between 3.58 and 1.73 were obtained o o for bench face angles between 10 and 30 making this range least susceptible to failure even when inundation is considered. Consequently when mining commences, a utilization of slope angles ranging from 10 to 30 coupled with adequate drainage conditions like digging of perimeter trenches and use
80E
120E
120N
TERTIARY
COMPUTER MODELING OF SLOPE STABILITY IN MINING THE TAR SAND OF DAHOMEY BASIN, SOUTHWESTERN NIGERIA
David Afolayan ALAO and Mopa BASSAGI DEPARTMENT OF GEOLOGY AND MINERAL SCIENCES, UNIVERSITY OF ILORIN P.M.B. 1515, ILORIN, KWARA STATE, NIGERIA
Abstract The need to have stable slopes in open pit mining of the tar sand deposit of the Dahomey Basin, Southwestern Nigeria is emphasized in this study. In the Loda village, Southwestern Nigeria, samples of the lateritic soil and alluvial sand which overlie the tar sand occurrence were subjected to geotechnical tests. Computer simulation of bench face angles was carried out using the SLOPE/W software to determine the bench face angle(s) with the least susceptibility to failure. Slope failure might lead to loss of lives and valuable heavy equipment thus increasing overall expense of running the mine. Geotechnical tests carried out helped to determine the unit weight (g), cohesion (c) and angle of o friction (f) values. For the lateritic soil, g = 25 kN/m3, c = 45 kPa and f = 41 . Also, values of g = 18 3 o kN/m , c = 0 kPa and f = 34 were obtained for the alluvial sand. These values were inputted into the software program to simulate different bench face angles that could be cut into the two lithologic o o units. Factor of safety values were obtained for 10 to 90 bench face angles at 1 metre, 4 metres and greater than 40 metres ground water level, respectively. 10 metre bench width and 6 metre bench height were used while 20 metre bench width and 6 metre bench height were also utilized to make room for heavier equipment. Factor of safety values ranging between 3.58 and 1.73 were obtained o o for bench face angles between 10 and 30 making this range least susceptible to failure even when inundation is considered. Consequently when mining commences, a utilization of slope angles ranging from 10 to 30 coupled with adequate drainage conditions like digging of perimeter trenches and use