Drilling and blasting improvement in aggregate quarry at Thailand - a case study

Abstract

World class infrastructure around Bangkok is developed due to medium to large aggregate quarries situated up to 200 km from Bangkok utilizing granite, limestone and basalt as resource. Aggregate consumption will be exceeding 350 MTPA by 2019. Aggregate quarry under study has proposed increased production from 2.5 MTPA to 5 MTPA. Drilling and blasting accounts for 28% of total quarrying cost based on the study of various aggregate quarries in Thailand. Powder factor values (P.F.) is 0.40 - 0.66 kg/m3 at 80% passing over 0.5m. Considering drilling and blasting as major cost, existing practices of drilling and blasting are reviewed. Top hammer (TH) 102mm diameter drill is selected as compared to existing down the hole (DTH) 76mm diameter drill. For large quarries 6m × 7m is blasting pattern as optimized with 150mm diameter drill. Projected blast pattern is 4m × 4.75m. TH, DTH, rotary cutting and rotary crushing drills are evaluated. Some of the best practices at an aggregate quarry in Thailand for drilling include drilling accuracy, bench’s surface flattening by auto leveling. Blast performance is monitored for blast fragmentation, back break. Nonelectric detonators instead of electrical detonators and bulk emulsion instead of ANFO shall be utilized for future blasting operation.