In open pit mining, the D&B technique is predominantly employed for breaking rocks through the application of explosive energy that fractures rocks to facilitate mining (Lapčević et al., 2023). The D&B QC necessitates the definition of two important concepts: fragmentation and muckpile geometry. Fragmentation pertains to the fragmentation of the blasted rock that is important for the efficiency of subsequent crushing and milling. On the other hand, muckpile geometry describes the shape and looseness of the rock after blasting, and it determines the productivity of loading machines. Attaining targets of both is only possible through strict QC procedures.
The first step towards achieving good blast performance is to have proper drilling. This is done by confirming whether the blast hole collar locations, angles of inclination, and depth of drilling match exactly the planned blast pattern. Drilling errors especially on the burden and spacing of drill holes significantly change the distribution of explosive energy within the rock mass (Shehu et al., 2021). Incorrect drilling results in irregular breakages of rocks into oversized boulders or too many fines.
QC is needed for explosive loading just as much as it is for drilling. The powder factor, which is defined as the amount of explosives loaded per volume of rock, should be determined based on the mechanical properties of the rock being blasted (Shehu et al., 2021). The result of underloading is insufficient fragmentation and a compact muckpile that makes digging difficult. Overloading results in wasted materials, dispersed muckpile, and flyrock.
In addition to this, the quality control at D&B is dependent on accurate sequencing of initiation and the timing of delays. Through the management of millisecond intervals between explosions of individual blast holes, the movement and interaction of stresses can be controlled. With proper delay timing, each blast hole is able to fracture into the desired free face configuration.
Post-blast assessment plays a critical role in continuous improvement. Operations have started to adopt the use of computer software to analyze digital images in order to determine the true size of the fragments quickly and safely (Shehu et al., 2021). A comparison of the real fragmentation and muckpile profiles with the prediction models helps mining engineers confirm and calibrate their blasting parameters.
To sum up, the D&B quality control process in open pit mining effectively ties in the theoretical process of blasting design with actual practice. With careful regulation of drilling precision, powder factor, and delays, the fragmentation and geometry of the muck pile can always be optimized. This will result in reduced costs for loading as well as increased efficiency in the crushing process.
References
Lapčević, V., Torbica, S., Stojanović, M., & Vojinović, I. (2023). Development and validation of universal 3D blast fragmentation model. Applied Sciences, 13(14), 8316. https://doi.org/10.3390/app13148316
Shehu, S. A., Mohd Hashim, M. H., & Awang Kechik, N. A. H. (2021). Preliminary assessment of the effects of blast design factors on fragmentation at Lafarge Kanthan limestone quarry, Chemor, Perak. ASEAN Engineering Journal, 10. https://doi.org/10.11113/aej.v10.16598
