Mining Project: Blast Damage Control to Reduce Injuries from Ground Falls in Underground Western U.S. Hard Rock Mines
To make available an easy-to-use software tool that includes improved blast damage models that mining engineers can use in developing improved blast designs. The improved designs would include decoupling the perimeter holes and properly locating buffer holes to reduce perimeter damage. With this design guidance, it will be easier for engineers to implement controlled blasting methods.
Editor's Note: The Beta version of the DRIFT software is being released in advance of SME 2018.
Today, ground falls continue to be of major concern to miner safety. Risk exists at the drift face where the miner is responsible for drilling, blasting, rock scaling, and installing roof support. The proper design and execution of drifts will become even more important in the future as mines become deeper, rock mass/stress conditions grow more complex, mining scale increases, development rates are increased to improve profitability, and the demands for safe execution, safe operation, and minimum opening maintenance become ever greater.
The centerpiece of modern drifting is the drill jumbo, allowing the operator to drill complex patterns and to complete the drilling quickly and easily. Although drilling has improved, controlled blasting is not widely practiced in the mining community. Controlled blasting reduces perimeter damage, and less perimeter damage means lowered risk of ground falls, especially during scaling and installing roof support. A well-blasted drift requires less scaling time and less troublesome ground support installation. The reduced exposure time during these tasks reduces the risk of ground fall injury.
Rock blasting techniques in underground metal/nonmetal mines need to be optimized to minimize the extent of loose and/or damaged rock surrounding blasted openings. This optimization could significantly reduce mine worker exposure to ground fall hazards. Optimization techniques are design-based. In most underground mines, loose ground on the back/roof and ribs is removed by hand scaling or mechanical scaling. From a safety perspective, while scaling ultimately reduces the risks of rock fall injury to the mine workers, the personnel responsible for scaling are at risk for injury when performing this task. The longer it takes to scale and support damaged openings, the higher the potential risks to workers. Poor blast designs, poor quality control, or the presence of unknown geologic structures can lead to excessive overbreak and even cause damage to adjacent ground that has already been supported. This is a significant problem with respect to both mining safety and operational efficiency.
The project aim was to provide industry and mine research institutions with detailed information on perimeter-controlled blasting and blast damage models that support perimeter control design. Toward this aim, a blast design software tool was completed in collaboration with the Colorado School of Mines and Hustrulid Mining Services. The software is suitably called DRIFT and allows the user to input blast design parameters and visualize the damage extents in a specific design. Automated design approaches include (1) the Holmberg design with reduced perimeter charges only, (2) the buffer design that reduces charge concentrations at the perimeter and in the second row of holes from the perimeter, and (3) the charge region design that institutes attributes from both the Holmberg and buffer row designs. A manual design option is offered where the user can input charge holes manually or switch from one of the automated approaches and make modifications by moving, adding, or deleting holes in the design.
Practical damage limit circles are drawn around each blast hole showing predicted damage extent based on a chosen blast damage model. The buffer row design specifically uses these damage circles to develop the design pattern.
A beta version of DRIFT is available for download and testing (see link below). A final version will be available later in 2018. Send any questions or comments regarding the DRIFT software to firstname.lastname@example.org.