Ensuring good slope geometry is arguably one of the most important activities for unlocking a mine’s value. In Peru, where this project begins, we finnd an open-cut copper mine producing

roughly 100,000 tonnes annually. Operators here place a high level of importance on maintaining healthy and stable slopes. One way the operation achieves this is through the regular use

of end-of-phase blasting practices. In recent times however, these blasts had begun resulting in excessive material movement, with multiple instances of displacement causing material to spill toward the bottom of the pit. This created

blockages along ramps, delayed site traffic, and diverted resources away from other operational areas to manage clean-up efforts. Most importantly of all, the spillage was contributing to significant ore loss.

‍

In response to the ore loss issue, the operator initially introduced a buffer row close to the free face. While the results from this adjustment showed improvement, they were not sufficient enough to completely mitigate the problem. At this stage, MTi’s Engineering Solutions team was engaged to provide a technical assessment and identify a potential path forward.

Through discussions with site personnel, a detailed understanding of the blasting conditions and geological environment was developed. Particular attention was given to both the Sulphide and Hydrothermal domains, with these discussions contributing significantly to understanding how and why the material loss was occurring.

Having identified the geological factors influencing the spillage, MTi recommended a modified version of the existing blast design. The revised approach incorporated both airdecking and timing adjustments to better control blast movement and energy distribution

‍

Using MTi’s proprietary numerical modelling tools, a revised blast design was developed that built upon existing site practices while introducing several key modifications.

The first change involved incorporating airdecks into the row closest to the crest. By reducing the explosive column in these holes, the design was able to lower excessive energy while still maintaining sufficient power to achieve the required fragmentation.

The second adjustment introduced an additional buer row between the existing buer row and the production holes, creating greater separation between the active blast energy and the free face.

Finally, the firing sequence was modified to redirect blast movement inward. This allowed the blasted rock to move more freely toward the inside of the bench rather than toward the pit bottom, reducing the likelihood of material spilling beyond the intended zone.

Following the modelling phase, the revised design was implemented across all interphase blasts. Spillage and blast movement were then monitored using video recordings, muckpile surveys, and specialised analysis software. The collected data was assessed to evaluate the effectiveness of the new design and quantify improvements in blast control.

‍

‍

‍

‍

Over the course of 17 blasts, both the new and conventional designs were tested and evaluated to provide a clear head-to-head comparison. Baseline analysis of 10 blasts using the conventional crest-control design showed a weighted ore loss of 8.83%, equivalent to 216.7 t/m of interphase spill. Following implementation of the new air-decked buffer-row design across 7 production blasts, weighted ore loss was reduced to 1.91%, while spill intensity decreased to 78.1 t/m. This represents a 78% reduction in weighted ore loss and a 64% reduction in spill intensity per metre of interphase. Fragmentation performance was also assessed, with results showing an increase in average P80 from 8.1 to 9.7 inches, while the average dig rate decreased slightly from 5,565 t/h to 5,432 t/h.

‍