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Blasting in quarries with RIOFLEX

From our experience, quarry shots are small shots (5-20 tonnes), in medium diameters (76-102mm) of hard rock (basalt, granite, etc) types. Typically, the crushing plant will define what is the maximum fragment size allowable. Anything above this optimum size (oversize) has to be broken at a great expense. On the other hand, excessive fines find their way to the scalps pile which keeps on building up at a huge and sometimes underestimated cost.

In our view, the needs for a quarry as far as explosives performance is concerned is:

  • uniform and consistent performance;
  • minimal oversize;
  • minimal fines;
  • maximum fragmentation between the fines and the oversize cut-offs;
  • maximum diggability and heave;
  • minimal overbreak;
  • minimal toe;
  • clean, regular faces and floors; and
  • minimum cost.

A few design characteristics will be necessary to satisfy these requirements:

  • Increase patterns to the maximum allowable. This will reduce the amount of fines because the number of holes necessary for a given volume of rock decreases. Increasing patterns translates into putting as much energy as possible into the hole whether it is achieved by density increase or by the energy content of the explosive itself;
  • Pattern expansion usually achieves minimum cost by reducing the drilling cost component of blasting rock;
  • Choose the explosive with the best balance of shock and heave characteristics that help to achieve the outlined requirements in terms of site-specific quarry needs;
  • Carefully control blast design. In particular, deviations with respect to established optimum designs. Variables to control include:
  • drilling accuracy : burden, spacing, depth;
  • explosive consistency;
  • accuracy of stemming lengths and stemming material; and
  • minimize subdrilling.
  • Constantly assess fragmentation, heave, diggability, etc, to fine tune patterns and general blast design;
  • Eliminate the effect of weather conditions and ground water in blast planning by using an explosive that it is specifically suited to all weather conditions. In our experience, quarry personnel tend to be very optimistic in evaluating the percentage of wet/dry shots or holes in a given shot. The reality is generally a situation with a higher percentage of wet holes than expected. This could blow any costings or budget estimates.

A bad explosive with a good design could produce a positive result while a good explosive with a bad design will not produce an optimum result.

In order to assess different bulk products the best approach is to do full scale field blasts with the explosives in question. Rather than relying on standard specifications which do not take into account the most important parameters that influence an optimum blast result such as blast design, rock type, weather conditions, crushing and loading equipment at the quarry, etc. Field evaluations will give you a better feeling as to what can you expect from a given explosive at a particular quarry. However, in the absence of field trials, you will have to rely on previous and/or current experience using different explosives or resort to standard specifications for your assessment.

RIOFLEX is being trialed constantly against competing bulk explosives in the quarry market. Our experiences during these trials generally result in the following:

  • No need for different patterns dry/wet
  • Pattern expansion : up to 30% (in some rock types)
  • RIOFLEX delivers excellent results in vertical or near vertical drilling (5 degrees) without increasing toe . This is the result of higher charge concentration in the bottom of the hole together with its inherent high energy. The quality of quarry faces also improves with smaller drilling angles. Near vertical drilling minimises chances of poor drilling.
  • Back break is not significantly affected by using RIOFLEX in near vertical drilled faces.
  • RIOFLEX allows for the reduction of subdrilling which keeps quarry floors in good condition for future drilling.
  • Accurate control of stemming lengths (+/- 0.1m) as chemically gassing is not used with RIOFLEX. This allows for an outstanding control of environmental side effects of blasting; vibrations and air blast.
  • Improved heave and muckpile motion. Flatter muckpiles better suited to front loading equipment.
  • Improved diggability and fragmentation
  • In the rock types commonly found in quarrying, a significant overall cost reduction is achieved:

    • + Reduced drilling cost (pattern expansion)
    + Reduced crushing costs (PRF)
    + Reduced costs related to minimum fines generation