By David Stewart and Tamara Wiseman

This paper examines how a proactive drill and blast optimisation programme using advanced technology will generate a measurably positive impact on primary crusher throughput ; reduction in secondary breakage and fines ; and improved efficiencies in the loading and hauling of shot rock .

quarry located in the south-eastern United States is a greenfield site established in 2011 . The quarry lies in the eastern part of the Georgia Piedmont area . It is within a distinctive , northeast-trending belt of relatively high-rank metamorphic rocks known as the Kiokee Belt , a poorly mapped sequence of units that largely consist of amphibolite , and various schists and gneiss that are host for relatively young granite bodies and associated pegmatite and aplite dikes . The operation is currently using a 50 ” × 62 ” ( 1.27m × 1.52m ) Jaw Crusher as their primary crusher and anything larger than 48 ” ( 1.22m ) is considered oversize . The operation is also using a Caterpillar 992K loader and two haul trucks : a Caterpillar 777 and a Komatsu 785 .

The operation was not achieving their desired production goals . Data collected during the benchmarking phase determined that production was averaging 932 short tons ( 845.5 metric tons ) per hour through their primary crusher . Target production for the crusher is 1 000 short tons ( 907 metric tons ) of rock per hour through the primary , with a goal of 65 000 short tons ( 58 967 metric tons ) per week . The quarry was unable to maintain this level of production on a regular basis . Along with production issues , the quarry was also experiencing extensive highwall damage , rolling floors , oversize , and hard digging at the toe of the highwall . Several potential causes for these issues were identified : geological

conditions such as prominent seams ; blast design and front row borehole placement ; and drilling accuracy . Figure 1 is an overview of the site .

The primary goals of the programme were uniform fragmentation , an increase in crusher throughput , improving the highwall by eliminating back break and back shatter preconditioning , and maintaining grade control through optimized drilling and blasting performance .

In conjunction with their drilling company , the quarry implemented a drill and blast optimisation programme using drill monitoring systems , drill navigation , a 2-D laser profiling system , 3-D photogrammetric profiling technology and borehole surveying equipment , and a GPS survey system . The deployment of the various technology was done in multiple phases as the need for more detailed profiles , blast design , borehole deviation , and blast performance analysis were identified .

Optimisation programme – Phase One

Phase One focused on the geological issues observed in the pit . Prominent seams located in the pit , which intersected with boreholes in a blast , allowed explosives gasses to vent through the blast face and adjacent boreholes during a blast .

The LIM system was implemented for drill monitoring . The system monitors drilling parameters such as tool feed pressure , air pressure , torque pressure , as well as tracking steel changes . This data can then be used to determine the depth where a cave or prominent seams intersect a borehole . This information is vital to ensure the appropriate weight of explosives or decking material is loaded in a borehole at the correct borehole depth . Figure 3 is an example of the report from the drill monitoring system .

Along with the drill monitoring data , 2-D profiles of the blast face were taken at individual borehole locations . These profiles were then used to adjust decking and explosives loading within the borehole . The adjustments demonstrated a visible reduction in the venting of gases through seams and out of the blast face , but only marginally improved crusher throughput and oversize reduction .

Because the initial Phase One changes showed only a marginal improvement in productivity and highwall improvement , a second phase of the programme was developed and implemented to address these areas of poor performance further .

Figure 2

12 _ QUARRY SA | JANUARY 2017