The Significant Reduction in Cost Price by Changing Excavation from Blasting to Mechanical Method Based on Rock Mass Properties in Sardar Bucan Limestone Mine

Changing excavation from drilling and blasting to mechanical method has many advantges related to the environmental health, safety, and economic benefits. The rock mass weakness degree due to the possibility of excavation by a bulldozer can be the important basis for the changing the excavation method. In adition, the cost price of each method is also an important criterion. The rock mass weakness degree can be investigated using rock mass properties such as uniaxial compressive strength (UCS) and discontinuity spacing or relatively lower limit of blastability index (BI) or at the higher limit of rock fragmentation index (RFI). UCS=13.38 MPa, discontinuity spacing<0.1 m, BI=20.33 and RFI=42 were obtained in Sardar Bucan limestone mine. The powder factors were also obtained 0.18 kg/m3 and 0.253 kg/m3 for using BI and RFI respectively. Drilling and blasting operations were carried out for using different powder factors espacialy for minimum powder factor of 0.253 kg/m3 with burden to blasthole diameter ratio of 42 corresponding RFI=42. The cost price was assessed 14434 Rls/ m3 (6443 Rls/ton) for powder factor of 0.253 kg/m3. Mechanical excavation using a bulldozer was applied to replace the method of drilling and blasting, and the cost price of excavation by bulldozer was obtained equal to 8319 Rls/m3 (3713 Rls/ton), which was 58% of the cost of drilling and blasting method at the optimized conditions. The possibility of changing excavation from blasting to mechanical method can be an important development in the safety, economic and environmental benefits.