عنوان مقاله [English]
The Rashakan limestone mine as supplier of Urmia cement plant is producing about 3 million tons of limestone ore. The proximity of this mine to the Urmia railway and the main transit road of Urmia-Mahabad, as well as the destructive effects of vibration and noise caused by mine explosions on residential and environmental area, has caused the use of continuous surface miner machines as one of options for continuation of mining operations. Determining the ease of rock mass extraction, which is referred to as the excavatability index, has a vital role in the decision making stage for the selection of methods and extraction machines. This paper investigate the feasibility of mechanized extraction based on the geomechanical characteristics of Rashtkan limestone mine rock mass. In 18 different sections of the of 8 geomechanical zones of the mine, geomechanical parameters including weathering, uniaxial compressive strength (UCS), joint spacing and layers thickness were measured by field and laboratory surveys. Based on the diggability index rating method, the excavatability of the zone (7), (1, 6), (8), (3 and 5) is classified in the hard, relatively hard, easy and very easy excavation classes. In the following, considering the uncertainties in the results of the classification systems, one of the most recent applied classification methods based on continuous rating is used. The results show that the estimation of both continuous and conventional rating methods for the three zones of 1, 6 and 8 is the same and for the zones of 3, 5 and 7, the continuous rating method suggests easier excavation condition. According to the results of this research, the geomechanical conditions of Rashakan limestone rock mass are appropriate for mechanized extraction and the use of continuous surface miner machines. It is recommended that in order to correct selection of the type and capacity of extractive machinery a technical and economic analysis be conducted based on the investment and the operational costs of each of the different options for different types of machines.