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Walter Madzimure is a seasoned Mining Engineer with over 18 years of experience in open-pit and underground operations, specialising in drilling, blasting, and explosives technical and sales. His career spans work across Zimbabwe’s asbestos, diamond, limestone, and coal mines in various capacities before focusing on drill-and-blast and explosives engineering for both surface and underground mines, including restricted areas. This extensive exposure has equipped him with deep expertise across diverse mineral commodities. He currently serves as Operations Manager at Intrachem Pvt Limited.
In this interview, Madzimure sheds light on optimum blasting.
How do you determine the optimal burden, spacing, and charge distribution for different rock types and bench heights in Zimbabwean mines?
We start by analysing rock properties such as density, strength, jointing and bench parameters like height. Using empirical design rules, we set initial burden and spacing, then refine through modelling and field trials. Performance indicators such as fragmentation, vibration, and throw guide adjustments to achieve safe, cost-effective blasts tailored to Zimbabwean conditions.
What key parameters influence fragmentation outcomes, and how do you measure and manage oversize or fines generation post-blast?
Fragmentation depends on how explosive energy is applied, and key to this are powder factor, charge distribution, timing, and rock mass characteristics. We measure fragmentation using digital image analysis tools like 3GSM and WipFrag software and validate with sieve tests. Oversize is managed by adjusting burden, spacing, and drilling accuracy; fines are controlled by avoiding overcharging and optimising timing. Secondary blasting or mechanical breaking addresses residual oversize.
How do you model and control ground vibrations and air overpressure to ensure compliance with environmental and safety standards, especially near sensitive areas or communities?
We use site-calibrated empirical formulas such as PPV for vibration and logarithmic decay for air overpressure, supported by software like Intrachem Austin Powder’s Paradigmn. Advanced models incorporating machine learning improve prediction accuracy. Control measures include optimising charge per delay and timing, with real-time monitoring via seismographs to ensure compliance.
How have electronic blasting systems improved timing accuracy, safety, and overall blast performance compared to conventional non-electric detonators?
Electronic detonators deliver millisecond-level timing precision, enhancing fragmentation and reducing vibration. They enable remote programming and blast circuit diagnostics, minimising misfires and improving safety. The result: better muckpiles, compliance, and downstream efficiency compared to conventional non-electric detonator systems.
What are the most effective strategies for minimising blast-induced damage to pit walls or underground structures, particularly in highly jointed or weak rock formations?
Accuracy in timing, energy distribution, and blast geometry is critical. Predictive modelling helps forecast outcomes and refine designs in any rock formations. Techniques like presplitting, trim blasting, and charge decoupling are widely used to protect walls and weak formations.
How do you balance explosive cost, powder factor, and productivity for optimal cost-per-ton?
It’s about the total cost, not just the explosive price. Higher powder factors may raise upfront costs but improve fragmentation, reducing secondary blasting and crushing expenses. Tools like Paradigmn optimise designs to find the sweet spot between energy input and overall productivity.
In your opinion, what things are small-scale miners doing wrong in blasting, and what can be done to make it right?
Common issues include unsafe handling and use of explosives, poor drilling, poor explosive selection and incorrect charging. Solutions start with acknowledging their role, then investing in training, licensing, and stakeholder support from government to suppliers to promote safe and efficient practices.
What advancements or best practices are you implementing to reduce flyrock incidents, noise pollution, and dust emissions during blasting operations?
We apply precise charge placement, proper stemming, and optimised timing to control flyrock. Noise is mitigated through delay sequencing, while dust suppression involves timing control and pre-/post-blast watering. Data-driven designs ensure site-specific solutions.
