The Impact of Blasting on the Business of Mining 1
C. P. Orlandi & C.K. McKenzie
2
Introduction The principal mission of the Mining Department is to provide to the processing plant a mineral in optimal condition for its subsequent treatment, either at the lowest cost or at the highest possible production rate, depending on the management philosophy of the mining operation. Of high importance also are the requirements to minimize the environmental impact, to ensure a strong community benefit, and to provide a safe and rewarding working environment. To win the mineral, it is usually necessary to remove large quantities of waste or low-grade material, the quantities of which are generally much greater than the quantities of ore being mined and processed. It is common, in the copper mining industry of Chile and Peru, to to have a stripping ratio in the order of 3/1; this being larger still in the mining of gold, reaching levels approaching 20/1. As far as the operations in the pit are concerned, the primary cost item then becomes the waste, not the ore, due to the greater quantities quantities and longer haul distances. It isn’t unusual to see the primary focus directed towards the production of mineral to the plant, while the extraction of waste attracts insufficient attention to permit optimization of the total mineral recovery process. The specific mission of blasting is, therefore, to pre-condition the rock, either mineral or waste, for its subsequent treatment in the most economical way possible for the whole business. The first step of the comminution process is blasting. This is nothing more than the application of external energy for the size reduction of the material. The task therefore, is to utilize the explosive energy in the most efficient means, such that all the subsequent processes can generate the highest possible possible value to the operation. In this this context, context, blasting complements the subsequent subsequent crushing and grinding stages of the comminution process, since breakage occurring in the pit represents a reduction in work required in the crushers and grinding circuits. When we speak of material pre-conditioning for its subsequent treatment, the first and obvious beneficiaries of optimized pre-conditioning are the excavators excavators and trucks. Well fragmented material promotes high shovel productivity, reduced truck loading times, reduced maintenance, and reduced wear rates on bucket teeth and tray bodies. The data is difficult to procure, but there is strong evidence (McKenzie, 2005,) that good fragmentation leads to reduced bucket-fill times ( Figure 2 ), increased bucket fill factors ( Figure 2 ), and reduced shovel and truck maintenance costs, and these benefits apply equally to both ore and waste. waste. The influence of fragmentation fragmentation is perhaps a little surprising when the size of the excavating equipment is considered – the data in Figures 1 and 2 were obtained from P&H 4100A shovels, and the estimated d 80 sizes (sieve size through which 80% of material will pass) for the material being excavated were estimated to be 150 mm (ore) and 400 mm (waste). Compared with the bucket size of 42 m 3, these blast fragment sizes seem small, but the data clearly shows a difference in terms of bucket fill times, bucket fill factors, and truck load times. The assertion that waste material does not require the same degree of fragmentation as ore may therefore be only partly true – if finer fragmentation in waste leads to lower removal costs and higher removal rates, the justification for finer blasting blasting in waste material may be easier to make. In the data obtained from this study, diggability (i.e. the tonnes loaded per bucket divided by the bucket fill time averaged over the entire blast) is 20 to 25% higher in ore than in waste. waste. If the waste could be excavated 20 to 25% faster, in line with shovel performance in ore, what additional VALUE would this bring to the total operation?
1
Enaex S.A., Chile (
[email protected])
2
Blastechnology, Australia (
[email protected] (
[email protected]); ); Cintex - Enaex, Chile (
[email protected] (
[email protected]))
C.P. Orlandi & C.K. McKenzie, McKenzi e, THE IMPACT OF BLASTING IN THE BUSINESS OF MINING
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Bucket Fill Time Comparison (Ore & Waste) 45%
Average (Ore) = 10.2 sec (909 trucks)
40% Average (Waste) = 11.9 sec (1324 trucks)
35%
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Ore Waste
10% 5% 0% 3
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11 13 15 17 19 21 23 25 27 29 31 Bucket Fill Time (s)
Figure 1. Comparison of bucket fill times for different materials.
Bucket Fill Time: Ore & Waste Comparison
Bucket Fill Factor: Ore & Waste Comparison
16.80
c 14.80 e s ( 12.80 e m 10.80 i T 8.80 l l i 6.80 F t 4.80 e k c 2.80 u B 0.80
1.10
Average (waste) = 11.9 sec Average (ore) = 10.2 sec
4 0 5 3 0 3 2
5 0 5 3 0 3 2
6 0 5 3 0 3 2
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2 0 5 0 3 3 3
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( r o t c a F l l i F t e k c u B
Average (ore) = 99.1%
1.05 1.00 0.95 0.90
Average (waste) = 91.6%
0.85 0.80 4 0 5 3 0 3 2
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6 0 5 3 0 3 2
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Blast No. W Was as te (Average = 11. 9 s ec )
Ore (Average = 99. 1%)
Was te (Average = 91. 6%)
Figure 2. Reduced bucket fill times and increased bucket fill factors in ore (powder factor 350 g/t) compared with waste (powder factor 250 g/t), based on several hundred truckloads for each blast (after McKenzie, 2005).
Other beneficiaries lie outside the confines of the pit, and include the primary crusher and even subsequent milling (SAG or AG mills). Studies have demonstrated the importance of the creation of micro-fractures in the mineral in facilitating both crushing and grinding (Nielsen & Kristiansen, 1996, Eloranta, 2001, Fribla & Orlandi, 2000, Paley & Kojovic, 2001, Katsabanis et al, 2003) through decreasing the “work index”, and likewise in the increased efficiency of leaching through the increased specific surface area (Fribla et al, 2001).
Production Chain v Value Chain The Mining Process, when considered in its full context, consists of many separate stages or subprocesses such as drilling, blasting, loading, hauling, crushing, grinding, flotation, etc. These subprocesses make up the Production Chain, and each one of the stages of a chain is needed for the creation of the final product. Each one of these stages must contribute VALUE to the business. Optimization has to consider the value and profitability of the total business, and not a focus on each operating unit in an individualized way. This realization leads us to the Value Chain, and requires a greater knowledge of how the various sub-processes react to various changes in the nature of the material being processed. It also requires that we define and quantify Value, consistent with the strategic objectives of the business and in terms of dollars, at every stage in the Production Chain. Each stage of the process must be optimized not for itself, but rather to maximize its contribution of value to the Global Process. C.P. Orlandi & C.K. McKenzie, THE IMPACT OF BLASTING IN THE BUSINESS OF MINING
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Generally in the mining industry, the objective of Operational Management is oriented towards the maximization of value, coinciding with maximization of production capacity, based on the optimization of the resources available. It is in the moment of defining the Mine Plan when it is possible to revise and integrate the external parameters with the direct production process. From this point of view, all that we produce in the various stages of the Production Chain are the intermediate products , whose optimum characteristics and properties must be defined in a clear and quantitative form. To achieve this, the Key Performance Indicators (KPI’s) must be defined. These must allow measurement of the grade of success achieved in the defined objectives for each stage, identifying the deviations and “learning from the errors and defects” to achieve consistency in the final product. The application of rigorous methods and up-to-date technologies is an absolute necessity for the success of these objectives, in particular for the transfer and the analysis of the information. We can summarize in the following way: An optimized management of the Global Mining Process – The processing plant must tend towards a maximization of value creation for the business, allowing a continuous improvement of productivity and a permanent reduction of operating costs, through the application of “state of the art” level worldwide mining practices. The necessity of a Global Management Model, integrating technical information and process economics, that considers from the Engineering design and appropriate equipment selection, to the Planning and Operation activities of the mine. Definition of an Integrated Mining Plan, that considers all the unit production processes, from Drill and Blast to the Processing Plant or in the case of waste material, the appropriate dump location. Incorporation of Current Technical Designs and the definition of Indices and Metrics of the Process Performance Evaluation, under the focus of creating value. Analysis of Parameters and Criteria of Planning and Operation with modern methodologies such as: Risk Analysis, Failure Mode Analysis, etc. Use of modern Information Technology, considering the installation of expert systems, with the ability of performance prediction, process control and reduction of the variation of the key aspects Permanent Benchmarking
The Objectives of Conventional Blasting •
Cost control...minimize unit costs.
The traditional focus of blasting has been the minimization of costs immediately related to the process, including drilling and explosives/accessories. Summarized, this means:
Produce a workable muckpile. Control environmental impacts. Minimize blasting cost. Avoid collateral damage.
Under this style of blast management, the bottom line is/was to minimize the budget without causing operational disruptions such as boulders for the shovels, fly-rock, toxic gases and excessive over-break. This style of management was perhaps appropriate before we had available the on-line monitoring systems (e.g. Dispatch) which now allow us to measure and track in real time the instantaneous performance of almost every piece of machinery in the mine. Often the Drill and Blast responsibilities in a mine are assigned to engineers recently graduated from university, and from this “convenient” position they can learn how the mine operates. It has been considered unnecessary to know why or how the rock is broken, or how to achieve a product C.P. Orlandi & C.K. McKenzie, THE IMPACT OF BLASTING IN THE BUSINESS OF MINING
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which has been specifically tailored to suit the next step in the Process Chain. That is, it often appears unimportant that the young blasting engineer cater to the needs of his down-stream customers. The sole interest is to minimize the cost of the Unit Operation. Likewise, it hasn’t been considered that the blast is a client of the drilling, and that the quality of the blasting is frequently controlled more by the quality of drilling than by the quality of the explosives. How many mines in our countries (Latin America) have a quantitative quality control program for drilling? How many mines yield, in an appropriate form, the geo-technical information of the rock, for further knowledge of the rock to be fragmented?
The Alternative View of Blasting Fragmentation...in accordance with Global Process Performance.
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If we consider blasting as an element in the Value Chain, we must define (or decide between the different clients and providers of the process) what is the value of the product, and how can that value be increased by changing how the blasting is conducted. Fundamentally, the objective of blasting is to break rock, thereby rendering it amenable to excavation and removal. Excluding maintenance issues, the cost to run an excavator is more or less constant, on a per-hour basis, with costs controlled by capital depreciation, labor, servicing, and energy costs. But the cost per tonne of material excavated will also depend on how many tonnes of material can be excavated per hour of operation, and it is here that the efficiency and intensity of blasting affects the Value of the process. $2.60
$3,900,000
$2.55
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e r O$2.50 e n n o $2.45 t / $ ( s $2.40 t s o C $2.35 g n i n $2.30 i M
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Total Costs
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Avg Powder Factor, Ore & Wa ste (g/tonne)
Figure 3. Cost minimization curve v Value maximization curve, as a function of the intensity of blasting (powder factor), after McKenzie, 2005.
Rather than striving to achieve “the cheapest tonne broken”, one can focus on the tonne that is the most economical, or the fastest tonne (i.e. the tonne of material that is most quickly loaded, most quickly hauled, most quickly crushed and most quickly passes through the grinding circuit), Figure 3 . This will be the tonne that complies with all the requirements of the Global Process, since it will produce higher productivity for the same capital expenditure. The qualities of this tonne of broken rock will be different for waste and for mineral, and as we are seeing, for different types of mineral as well. A process model combining blasting, loading, hauling and crushing operations ( Figure 3 ) highlights two important issues. Firstly, the average powder factor required to maximize Value is significantly higher than that required to minimize costs. Secondly, the slope of both curves is steeper before the turning points than after, highlighting that the penalties associated with underblasting are greater than those associated with over-blasting. But how many mine operators and mine managers prefer to err on the side of over-blasting than on the side of under-blasting? After only a preliminary analysis, it is clear that delivering the optimum feed to the grinding mills requires close liaison and communication between blasting engineers and primary crusher operators. Figure 4 shows the effect of the primary crusher on changing the size distribution of blasted material presented to the SAG mill for a soft ore, and a hard ore. Significant size reduction C.P. Orlandi & C.K. McKenzie, THE IMPACT OF BLASTING IN THE BUSINESS OF MINING
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(and value adding) occurs with hard ore, but little size reduction (and value adding) occurs in the crusher when processing soft ore. Blasting may be the only opportunity to effectively pre-condition soft ores, whereas the crusher can complement the blasting for hard ores. It becomes immediately apparent that blasting and crushing need to be coordinated, and it may be difficult for a crusher to simultaneously process two completely different ore types. Today, it is possible through the use of size distribution measurement tools based on digital images (WipFrag, Split, FragScan), to assess the blast on a quantitative basis, as opposed to the traditional qualitative and subjective evaluations. 100%
100%
Post Blast Sizings
g n i s s a P %
Crusher Discharge
10%
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Figure 4. Effect of the primary crusher on soft ore (left) and hard ore(right).
The Principal Blasting Constraint •
Control of Slopes... for the guarantee of safety and the viability of the Project
Fragmentation and breakage are the obvious, and designed outcomes of blasting. But breakage is not restricted to the zone of rock in front of a blasthole. The same process which causes fragmentation also causes damage behind the last row of blastholes, and this can impact on the stability of pit walls, and the safety of personnel and equipment working in the pit. Even single bench rock falls and failures can cause equipment damage, or injury and death to workers. Using practical engineering tools and models, it is possible to quantify the negative impact of the blast, and in doing so quantify the success of the blast in terms of geotechnical stability and safety. Today there exists a wide range of instruments that permit the accurate assessment of changes in rock quality and slope stability, thereby allowing confirmation of, or adjustment to, the slope design criteria or Risk Assessment programs.
Figure 5. Excellent quality smooth walls in Chilean copper mine, in heavily structured material. C.P. Orlandi & C.K. McKenzie, THE IMPACT OF BLASTING IN THE BUSINESS OF MINING
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Figure 5 highlights
what we believe is a false paradigm in porphyry copper type mines, typical in this part of the world. There are two primary factors explaining the commonly heard adage “in this mine it isn’t possible to have clean walls and half barrels....”. The first is a lack of understanding about the technical issues controlling the effectiveness of smooth wall blasting. The second is an absence of a Value Model which quantifies the benefits of clean and stable walls, and which permits a clear decision on appropriate expenditure to achieve the required results. How do we calculate the VALUE of clean safe walls with minimal deterioration of in-situ rock strength? When cleaner walls allow steeper walls, the value is easy to calculate and the dollar figure is large, so this catches the eye of most managers. When cleaner walls mean safer conditions, it is much more difficult to attach a dollar value – so we don’t usually try, and we generally focus instead on finding ways to produce final walls at minimal cost, which meet the approval of regulatory bodies. Once a decision is made as regards design slope angle, we quickly forget the assumptions of minimal disturbance to rock strength which are inherent in the pit slope design calculations, and almost never conduct measurements to confirm those assumptions. What is the VALUE of reducing the probability of failure by 30%, when pit slope angle has already been decided? What operations even MEASURE the degree and extent of damage induced in pit walls? Most smooth wall blast design philosophies address vibration control, with the implicit assertion that reducing vibration levels in the pit walls will reduce the extent of blast-induced fracturing, and the probability of block dislodgement (e.g. wedge failures, planar failures). Many articles have been written demonstrating the effectiveness of vibration reduction in the control of damage, suggesting that this is an area worthy of attention and measurement as a means of Quality Assurance. There is tantalizing evidence that we can quite easily detect fresh fracturing and fracture dilation occurring at any point behind blasts (McKenzie & Holley, 2004) and in this manner quantify the shape of damage profiles and estimate critical vibration levels which initiate either fresh fracturing or fracture dilation. This then permits 3 dimensional modeling of vibration in the zone behind blasts, incorporating the effects of pattern geometry, explosive distribution, delay timing, delay accuracy and initiation sequence, from which damage probability curves (i.e. the probability of exceeding critical vibration levels) can be established for any proposed smooth wall blast design ( Figure 6 ). This appears to be a powerful tool which permits a very comprehensive comparison to be made between various wall blasting options as regards the effectiveness of vibration control and the degree and extent of likely damage. But the basis for selection of the most appropriate design remains that of cost, because we are unable to determine the different VALUES that the various options bring to the Global Process. The cost factor may be overriding safety! 100%
) % ( e g a m a D f o y t i l i b a b o r P
90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 0
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Distance from Back Row (m) Design option 1
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Figure 6. Probability of damage as a function of distance behind back row of blastholes, for 2 different smooth wall blast designs (model results). C.P. Orlandi & C.K. McKenzie, THE IMPACT OF BLASTING IN THE BUSINESS OF MINING
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Impact of a Blast: Summary In Mineral: The Explosive provides the most economic energy for the fragmentation of the rock The blast is the most efficient stage of the Comminution Process, from both the technical and economical points of view (in value contribution) Blasting philosophies should be matched to rock characteristics. Finer is not always better, and modeling has advanced to a stage where it can provide very clear directions for identifying optimum rock-specific blasting strategies. There is now compelling evidence that more intensive blasting improves processes such as leaching, not only by producing finer material, but also through the increased generation of micro-fractures which further increase the available surface area for the chemical reactions to occur. Compelling evidence of the powerful leveraging effect of optimized blasting on loading, hauling, crushing, grinding, and maintenance costs, the benefits from which are likely to far outweigh the additional costs.
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In Waste: In the majority of the mine sites, more waste material is moved than mineral, and a proportionally large fraction of mining costs are associated with waste removal. Better blasting in waste allows increased loading rates, reduced hauling costs, a faster exposure of ore, and a greater resource allocation to ore handling. We should consider the impact of the fragmentation and muckpile swell on the costs of equipment maintenance. There are certain psychological effects as well: A shovel operator will take more time to load a truck if the size of the material can potentially damage the truck if loaded too quickly, that is letting the material drop without great care for the truck tray, so that fragmentation may also affect the bucket discharge time, not just the bucket fill time. There will be a limit as regards fragmentation in waste – if blasted too fine, the additional blasting costs are not recovered by reduced load and haul costs. The cost/benefit curves suggest that the risks associated with under-blasting are significantly greater than the risks associated with over-blasting. ⇒
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In the Safety and Viability of the Mining Project: With carefully controlled smooth blasting, it is possible to maximize pit slope angles, minimizing the effective strip ratio and improving the economic parameters of the investment. With effective smooth blasting it is possible to obtain clean and safe walls for both personnel and equipment, minimizing the risk of injury/damage. The probability of wall failure can be reduced by more effective smooth wall blasting, though the VALUE of the reduced probability can not yet be translated into a dollar figure. ⇒
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The impact of the blast in creating value remains clear if we define this Unit Operation (Orlandi 2001) in the Corporate Mission as: “ ...Pre-conditioning of the rock for its subsequent treatment....”. In this way, we must clearly identify the subsequent processes in the Production Chain for the material that we are going to blast, establishing indicators of specific achievement for both the waste and the ore. It isn’t the Drill and Blast Engineer who determines the characteristics that the blast product (that is the resulting muckpile) must have, but rather his/her customers. C.P. Orlandi & C.K. McKenzie, THE IMPACT OF BLASTING IN THE BUSINESS OF MINING
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The optimum fragment size distribution will be different for the mineral that goes to the plant, and for the waste that goes to the dumps. The size distribution required for the mineral will be also dependent on the type of processing, and/or the crushing and grinding equipment, and must be established for each respective customer, for each different mineral type and grade. For the ore, it is relatively clear how to define the optimum product size distribution, even though few operations have prepared this specification. However the definition of optimum waste characteristics to optimize excavation and transport, has not been clear in practice, in spite of the larger quantity of waste that usually is moved in open cut mining. This says we know more about what the Mill Customer expects than we know about what the Shovel/Truck Customer expects. The relationship between muckpile characteristics and shovel productivity remains largely unexplored.
Opportunity •
To maximize the benefits that the blast can contribute to the production chain, adding “value” to the blast product
The opportunities to maximize benefits to the Global Operation by more effective blasting must be embraced by those responsible for the Management of the Business. They must report to the owners or shareholders on the contribution of this process to total value, rather than on the technical or economic result of the unit process. It is their responsibility to develop the mathematical-functional model of the process, with the appropriate performance indicators that demonstrate the success (additional value) of the optimum balance. The principal direct impacts of a blast are shown as follows:
The blast adds value if: It allows an increase in the Processing Capacity of the Mill, the value of which exceeds the associated additional costs (increased profitability of recovery). high crusher productivity; high mill throughput; low maintenance costs; The pit wall design slopes are achieved. Operational safety is enhanced.
The Blast reduces value if: It causes a decrease in the Processing Capacity of the Mill, the value of which exceeds the associated cost savings (decreased profitability of recovery). reduced crusher productivity; reduced mill throughput; high maintenance and repair costs; The pit wall design slopes are not achieved. Operational safety is reduced. Environmental impact is increased.
The Role of Technology The primary tool used to estimate the likely outcome from a blast has traditionally been the simple powder factor (quantity of explosive per tonne or cubic meter of material). Combined with years of hard-earned experience and consistent geology, this simple parameter frequently provided quite reliable predictions of blasting outcomes. Today, it is rare to find consistent geology, and in many operations rare to find blasting engineers with more than a few years of experience. Further, we are expected today to have a much greater degree of control over costs and machinery C.P. Orlandi & C.K. McKenzie, THE IMPACT OF BLASTING IN THE BUSINESS OF MINING
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performance. Despite this, the humble powder factor still carries an inordinate weight in many operations, in which management cling to inherited paradigms such as “a powder factors greater than 0.6 kg/m3 is simply wasting money”. In many operations, a strong management focus is directed towards ensuring that the powder factor for each blast lies below an almost-arbitrary budget limit prepared without prior consultation with the rock. The potential for, and expectation of, more precise control over blasting outcomes has spawned technological innovation in blasting to the point where the availability of increasingly sophisticated technologies obliges a more profound characterization of the material to be blasted, as well as quantitative assessment of blasting outcomes. A rock mass is naturally a non-homogeneous and anisotropic medium, and its physical and mechanical properties usually vary throughout an orebody, significantly influencing blasting results in different geological domains. The use of appropriate tools is therefore required in order to quantitatively describe the relevant parameters of the rock that is to be submitted to the energetic and dynamic charge detonation. A reliable and comprehensive “blasting index” of the rock is needed, that is subject to current “state of the art” investigations in Blasting Engineering. Drilling provides an obvious opportunity to capture crucial information about the rock and its response during blasting, with the promise of allowing adjustment of the energy distribution during blasthole charging, though the goal continues to elude us. To extract the maximum benefit from the use of electronic initiation, for example, requires knowledge of what is being called the “Mechanical-Acoustic Model” that considers “non-traditional” parameters in our blast design deliberations such as: 1. Average size of the insitu blocks and their distribution or dispersion; 2. Orientation of the discontinuities 3. Acoustic impedance of the material The principal tools at our disposal to vary and tailor the results of blasting to match client specifications or expectations are:
Adjusting Powder Factors Adjusting the Distribution of the Charges Optimization of the Explosive Confinement: Stemming Reinforcement Aggregate (crushed material, gravel) Use of Variable Energy Explosives Aluminum Nitroparaffins (Comsol, NP-SERA) High VOD Explosives Oxygenation Variable density Micro-spheres Hybrids Diluents Air decks Exploitation of the Dynamics of the Blasting Process Initiation (timing, direction, sequence) Systems of Precise Initiation Computer models for Design, Analysis and Blast Simulation, such as QED Plus ® from Austin Powder, widely used in Chile, and JKSimBlast, from the Australian Institute, JKRMC. ⇒
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The Production Chain ... Is a Process of Transformation of Energy. An economic focus on the Mining Production Chain shows us that this is a Process of Energy Transformation, applied as a process of pre-conditioning via the reduction of material size and incorporation of micro-fractures, for its later physical and chemical treatment. That is to say, its transformation into a commercial product. The sources of energy are basically explosives, and electricity either generated in thermo-electric plants (petroleum, carbon, natural gas) or bought from public networks. The understanding of the Energy Balance of the global process is a powerful management tool. Various publications show that the proportion of the cost of energy necessary to induce a change of similar proportions through explosives, in the mine, crusher and grinder is in the order of 1 / (4-6) / (8-12), for a wide range of types of rock and industrial equipment. This indicates that the blast is the most efficient step in the comminution process. In any case, we need to know more, however we can’t import the knowledge or experience from other environments, other rock, other equipment, and other circumstances. We need to generate it from our own mines and situations. In an established operation it isn’t easy to determine the optimum relations between the different unit operations. In spite of the existence of specialized instrumentation and platforms of communication for gathering on-line, real time performance data from equipment, we frequently give little priority to the task of transforming this data into useful information for the Management Team. The work methodology that can assist us to advance in the understanding of our Global Process, and the impact of each one of our own activities in incorporating value is based on Groups of Continuous Improvement. In this respect, there have been various successful experiences in Chile, that have assisted the respective mining companies to be leaders on a world level in the mining of copper. The authors are sure that there doesn’t exist an appropriate way to incorporate technologies of the latest generation for the improvement of our business, without previously assuring that we have the resources to extract the benefits of the new technology. Why purchase a new on-line data system, if we don’t have the resources, commitment, or tools to utilize the new information? We should be able to anticipate the benefits to the Value Chain and the Improvement Cycle, and clearly define the requirements for the new technologies and support systems.
The Improvement Cycle. In the administration of a Continuous Improvement Group in a mine, where it is assumed the blast is the process initiator, it is fundamental to highlight the idea of “negotiating” the objectives expected of the blast between its different clients. These departments are principally: Planning, Geology, Geo-technic, Operations and Plant. The requirements of these clients are sometimes conflicting, but we must search for the optimum for the global operation, not that of the client with the most power or influence in the organizational structure. For example, the demand for “meters drilled” will not guarantee a good location of the hole, the precision of its angle or its correct depth. There seems to be little awareness of the importance of Quality Control in drilling in achieving the expected result of a blast, and many operations immediately focus on the explosive as “the guilty party” when results are unfavorable. It is very common to observe that the factor having the greatest impact on blasting results is the quality of the design implementation and drill plan rather than the explosive itself (type of explosive, powder factor). In an analogous form, the success of slope control is frequently related to the inefficiencies of the Production Equipment. Stop the extraction because the shovel reached the designed bench line, C.P. Orlandi & C.K. McKenzie, THE IMPACT OF BLASTING IN THE BUSINESS OF MINING
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even if it can easily remove more material? Carry out buffer blasts or pre-splitting in small diameters even if the available equipment has larger diameters and is more efficient? A short term decision, such as complying with the daily extraction goals, can sometimes prevail over the longer term interests, such as the slope quality and its impact on “the bottom line” of the Statement of Results of the company. This, although it may be a trivial problem, is a complex situation. A change that can seem technically obvious is often in reality impractical if it wasn’t foreseen and addressed appropriately in the Mining Plan. It isn’t always possible to acquire or contract additional equipment, such as drills with a smaller diameter, loaders to clean the walls or backhoes to clean the “crests”. There also exist contract type restrictions such as the productivity bonuses of the equipment operators, which generally don’t consider work quality indexes, but rather only production volume. These are, in short, perverse incentives that can have complex negative impacts on the optimization of the business. Generally speaking, there is limited knowledge in the mining industry of the physical fundamentals of the daily phenomena that we confront. Few professionals make decisions with regard to knowing or referring to themes such as wave propagation or fracture theory. There is a tendency to regard specific experiences as representing inexplicable departures from the universal concepts of physics, without considering the characteristics of each case. “In our mine things are different...” is the excuse in many cases, to evade the responsibility of investigating and understanding the problem. It is clear that it is not always possible in practical terms to apply sophisticated concepts as useful tools to the management of a business. However, on the other side, neither is it possible to bend the Laws of Mother Nature. The way that we see, in the short term at least, is to establish cause and effect relations between the parameters that we have the capacity of measuring and adjusting in the operation and relate these to the measured and predicted results. The current information systems and data administration systems should have the capacity to allow a complex analysis of the variables of the mining process as a whole. Importantly, we must learn to use the data we are constantly gathering (e.g. Dispatch High Precision Data), and to transform the data into information upon which decisions can be made by use of Process Models. The application of statistical tools, together with the ability of computational simulation should allow the integration of the majority of the unit operations into a complex but useful network. Today we have the use of innumerable support tools, instruments and software, to model “our” process and the power to incorporate these sophisticated procedures of analysis and control, with support systems of the latest information technology (Risk Analysis, Failure Mode Analysis, Tendencies/Trends Analysis of Active Parameters of the Process, Systems for Fragmentation Assessment through Photo-analysis, Registry Systems of Equipment Vital Data , Simulation of the Blasting Process Systems, Systems of Structural Mapping in 3D; etc.) Our challenge is to develop an Expert System, combining artificial intelligence and our knowledge, that will allow control of our Mining Process (Mine – Plant – Market), to achieve the maximization of the value incorporation as a product of management excellence. The pre-requisite step will be to learn certain techniques such as “fuzzy logic” and neural networks so as to improve our knowledge of the phenomenology of the processes themselves.
Summary
The Blast, as the first stage of the rock comminution process, has the mission of pre- conditioning, or preparing, the rock for its subsequent processing, in order to obtain a commercial product in the most economic way possible. It is necessary to know (=quantify) the impact of blasting on the processes of loading, hauling, crushing, and grinding, as well as in the movement of waste material (productivity of extraction equipment and transport).
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Today, we know too, that we can impact on aspects such as the efficiency of leaching, using appropriate explosives and systems of high precision initiation It is necessary to define the relevant Key Performance Indicators of the mining process: fragmentation (size distribution), pre-conditioning (reduction of the Work Index), swell of the muckpile, damage to the walls, dilution, energy consumption, and impact on the environment and personnel, e.g. dust) A system of measurement should be implanted to continually assess these parameters: “that which cannot be measured, can not be controlled”. It must be linked with the Mining Plan and correctly implanted for the value creation of the business throughout the Production Chain. A missing link in the Value Chain is our ability to quantify the VALUE of improved pit wall stability, and reduced probability of failure, in dollar terms. Until we can do that, we can not make properly informed decisions regarding wall control blasting. Further development in Quantitative Risk Assessment would appear to be a high priority.
References Eloranta, J., 2001. Improve Milling Through Better Powder Distribution , Proc 27 th Annual Conf. ISEE, Orlando, USA Jan 28-31, pp 55-63. Fribla, M., Orlandi, C., 2000. Effects on Economics in the process of optimization of the specific load of explosive and its relation with the micro-fractures generated through Blasting, 2 nd Jornadas de Tronadura ASIEX 2000. Fribla, M., Navea, D., Orlandi, C., 2001. Micro-fracturing Produced by the Explosive and the Increase of the Dissolution of Metal in an Oxidized Copper Ore , 3 rd Jornadas de Tronadura ASIEX 2001. Katsabanis, P.D, Gregersen, S., Pelley, C, and Kelebec, S., 2003. Small Scale Study of Damage Due to Blasting and Implications on Crushing and Grinding , Proc 29 th Annual Conf. ISEE, Nashville, USA, Feb 02-05, pp 355-364. McKenzie, C.K., 2005. Blasting – A Focus on Value , ASIEX Conference 2005, Viña del Mar, Chile, May 25-27. McKenzie, C. and Holley, K., 2004. A study of damage profiles behind blasts , 30th Annual Conf. ISEE, New Orleans, USA, Feb 01-04, pp 203-214. Nielsen, K., and Kristiansen, J., 1996. Blasting-Crushing-Grinding Optimisation of an Integrated Comminution System , Proc Fragblast 5, Montreal, Canada, pp 269-277. Orlandi, C.P., 2001. Precise Initiation, Blasting for Open Cut Mining Conference, ASIEX, Iquique, November 28-29. Paley, N. & Kojovic, T., 2001. Adjusting Blasting to Increase SAG Mill Throughput at the Red Dog Mine , Proc 27th Annual Conf. ISEE, Orlando, USA, Jan 28-31, pp 65-81.
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