The stability of slopes depend on the geological structures, geomechanical properties of the slope materials and groundwater condition in the mine. The present research paper deals with the determination of the optimum overall slope angle at Donimalai Iron Ore Mine. It was also aimed to know the influence of slope design parameters on the safety factor by sensitivity analysis, which tells the importance of the parameter in the slope. A more justified and suitable remedial measure can be planned for any critical slope after sensitivity analysis. Donimalai Iron Ore Mine is a fully mechanised mine and forms a part of Sandur synclinorium of Bellary - Hospet range in Karnataka state of India. It has high grade hematite ore. It is producing yearly about 3.8 and 1.8 million tonnes of ROM and waste respectively. The iron ore deposit of Donimalai occur at the top of the series of ridges running NW to SE and rising to more than 1000 metres above mean sea level. In view of the geological setting of the deposit, considerable amount of side burden removal is to be undertaken. The direct shear strength test was conducted to determine the cohesion and internal friction angle along joint planes. Initially kinematically possible failure modes were identified. The slope stability analysis was done for the optimum slope design. Based on the present study the ultimate pit slopes of both the 2E and 3W mines of north block were designed with 55° overall slope angle. The same deposits were being mined at 45° overall slope angle before this geotechnical study.
The stability of the slope primarily depends on the orientation of the discontinuities of the planes, strength properties of the slope materials and groundwater condition within the slope. Initially kinematically possible failure modes are identified. Then, detailed slope stability analysis is carried out by limit equilibrium method. Donimalai Iron Ore Mine is a fully mechanised mine and forms a part of Sandur synclinorium of Bellary - Hospet range in Karnataka. It has high grade hematite ore. It is producing yearly about 3.8 and 1.8 million tonnes of ROM and waste respectively. The production cost of ore is Rs. 152/- per tonne. The mine consists of six deposits, 1 & 1A in the south block, 2E & 3E on the eastern side and 2W & 3W on the western side of north block. The Donimalai deposits are situated on the southern half of the eastern range of hills flanking Sandur valley. The Iron ore deposits of Donimalai occur at the top of the series of ridges running NW to SE and rising to more than 1000 metres above mean sea level. The region has a hot and arid climate. There is an acute scarcity of water in this region. There are no perennial streams or springs. The average annual rainfall from the year 1987 to 1997 is 900 mm, with a maximum rainfall of 1168 mm in the year 1993 and a minimum of 647 mm in the year 1989.
