Point of Beginning

An Explosive Field for Surveying

October 4, 2012
Accurate measurements and detailed 3D models are crucial for improving drilling and blasting operations in mining.

This stock image of a mine blasting operation shows what happens when blasting is done incorrectly.

It might not be obvious from a distance, but mining is a precise business. All the drilling and blasting required to extract valuable raw materials must be meticulously planned ahead of time to maximize profitability, ensure worker safety and minimize environmental impact. The use of accurate design metrics is therefore imperative.

Lafarge, one of the world’s largest producers of cement, aggregates and concrete building materials, operates 600 mines sites globally. Recognizing the important role that measurement plays in mining, the company has implemented an initiative to employ some of the latest profiling and measurement technologies to optimize its drilling and blasting operations.

The company began the initiative with a pilot study across 12 sites. Mine faces were prepared by clearing the benches, scaling loose rock and inspecting bench condition. Particular attention was given to the precise measurement of the burden on the first row of holes. “Accurate bench profiling and surveying is the first stage in the manufacturing process and is critical to the efficiency of the remaining downstream activities,” says Xavier Thérin, vice president of land, minerals and mining for Lafarge. “Key to this is the use of correct equipment and trained operators. Measurement of bench heights, level of crest and toe, slope angle, and maximum and minimum burden can be done using 2D and 3D laser profiling.

“By mapping a rock face in detail, it is possible to determine actual burdens in front of each planned borehole to avoid excessive burden (vibration, oversize) and insufficient burden (flyrock, airblast). If neglected or if surveying is done incorrectly, it can have a detrimental effect on the rest of the manufacturing process including poor quality drilling and mining operations with increased safety risks and cost.”

Accurate measurement is imperative for a successful blast design.

Based on the quarry face profile data, blast hole layouts were designed, taking into account safety parameters, vibration limits, the explosives to be used and design floor elevations. The resulting blast design plans specified the collar elevations, burden, spacing, drill hole diameters, type and quantity of explosives, and type and delay of the detonators. The layout of the blast hole pattern was then established using surveying instruments. “Blast hole layout should be designed with respect to the collected survey data,” explains Thérin. “Hence, the accuracy and interpretation of this data is paramount.”

With the layouts in hand, the teams next used MDL’s Boretrak system to measure up hole and down hole geometry to ensure that the drilling would proceed as planned. “Checking that the drilling is done correctly as per the blast design is very important, including verifying the hole depth, diameter and inclination using accurate blast hole geometry measurement equipment,” Thérin says. “Incorrect drilling, including wrong positioning, incorrect angle, hole deviation, and incorrect depth, can pose serious risks.”

In a final step, the teams implemented a loading plan that optimized the position of delays, charge, charge distribution, type and quantity of explosives, as well as stemming requirements.

According to Thérin, the goals for an optimized drilling and blasting operation included reducing costs for blasting and drilling, improving loading speeds, reducing oversize breakage and handling, reducing energy consumption and reducing fines. The pilot study at the Lafarge mines showed substantial benefits in all of these areas by using the advanced profiling and measuring technologies.

“The average measured saving from the pilot study across 12 sites is about four Euro cents per tonne,” Thérin says. “Across Lafarge’s total aggregate and cement mined tonnes (250 Mt), this equates to a 10 million Euro savings annually. Lafarge is confident that further savings can be made through a rigorous optimization process and is currently rolling out the system across the group.”

For more information about Lafarge, visit www.lafarge.com. Additional details about MDL laser measurement technologies can be found at www.mdl-laser.com.