18? International Mining Congress and Exhibition of Turkey-IMCET 2003, <© 2003, ISBN 975-395-605-3 Possibility of Using Mechanical Miners in Underground Chromite Mines' Ore Productions and Two Different Examples H.Tunçdemir, H.Çopur, C.Feridunoğlu & N.Bilgin Department of Mining Engineering, Istanbul Technical University, Istanbul, Turkey ABSTRACT: Metallic ore prices have been decreasing recently due to unstable supply and demand relations and developed recycling methods of scrap metals. Therefore, Turkish underground metal mines and produc- tion methods should be reviewed especially in terms of economical ore cultability. Rapid and productive technologies should be applied as soon as possible to reduce production costs and increase competitiveness. For this purpose, it has been investigated that whether mechanical miners could be used for production and development purposes in chromite mines. In order to realize full-scale cultability tests in the laboratory, pri- marily miscellaneous investigations were performed in two different chromite mines: Kayseri-Pulpinar and Eskişehir-Kavak. Some information was obtained about production methods and working conditions and then, ore and country rock samples were collected from. After defining optimum cutting conditions, mechani- cal miners' production rates were estimated via performance prediction methods. Consequently, it has been found out that a mechanical miner could produce approximately three times more chromite than existing mining methods. 1 INTRODUCTION The necessity of high investment in mining industry dictates mechanized excavation for efficient mining to reduce operating costs. Due to this fact, exploita- tion methods of different mines in Turkey such as chromite mines have to be revised for more efficient mining operations. Recently, metal prices in world slock market de- creased considerably (Sullivan and others, 2001). The use mechanical excavators such as roadhcaders, hydraulic hammers, etc have the potential to increase productivity, since ihey have continuous, flexible operation capabilities to adapt to existing methods. Some applications of mechanical excavators for ore excavation were reported to be successful (Atlas Copco-Robbms. 1996, Breitrick, 1998). In order to investigate the possibility of using mechanized excavators in metallic ore formations, first physical and mechanical properties of the ore have to be determined in the laboratory and in situ such as schimidt hammer rebound value. Rock mechanics tests, such as uniaxial compres- sive strength (UCS), tensile strength test (TS), Cer- char ahrasiviiy lest, static and dynamic modulus of elasticity give preliminary assestment for the machi- nability of the geologic formation. However full scale cutting tests are strictly advised to be carried out for efficient selection of mechanical excavators in optimum conditions. 2 OBJECTIVE OF THE STUDY In-situ and laboratory tests are performed to investi- gate the possibility of using the roadheaders and hy- draulic hammers for ore excavation. Objectives of the study are given below. • Investigation into cutting mechanics ol chromite ores and surrounding rocks in se- lected mines, • Methods of reducing operational costs and investigating applicability of mechanical ex- cavators such as roadheaders and impact hammers in selected mines. 3 .THE EFFICIENT USE OF MECHANICAL EXCAVATORS IN ORE EXCAVATION Underground excavation methods are grouped as drill and blast and mechanized excavation. Drill and blast has coarser muck lhan mechanical excavation thus making it more efficient from specific point of view. Low advance rate, vibration and support 135