Advances in design technologies in drill, blast and conveying

Part of this process is already being achieved in mining operations in simple stratified geological settings like Rio Tinto?s West Angelas iron ore mine in Western Australia but the variability of the rock being quarried in itself poses technical challenges to the ultimate quarry.
The use of technology in quarry design is becoming more important as the process of data collection within quarry operations improves and the technology of quarry equipment improves. Major breakthroughs directly related to design include the use of Global Positioning Systems (GPS) on quarry equipment, the use of Measure While Drilling (MWD) technology to obtain geological and geotechnical data from the drilling process and direct geotechnical monitoring of hazardous areas.

DEVELOPMENTS IN THE AUSTRALIAN MINING INDUSTRY
The quarry industry is seen as the ?poorer brother? of the mining industry and quite often the levels of capital expenditure for new technology that may be made in the mining industry are not justified in the quarry industry. 

Following a successful two-year trial at the West Angelas mine,  Rio Tinto plans to double its fleet of driverless haul trucks at its  iron ore operations in Western Australia (Rio Tinto, 2011). The broader operational deployment of the autonomous trucks marks a step forward in the development of the Mine of the Future vision, delivering improved safety and production efficiency in haulage.
An integral location for Rio Tinto, the West Angelas site has taken on an acute technology focus that includes the development of a remote operations centre (ROC) in Perth that will eventually control trains, drills and trucks from as far as 1300km away. Rio Tinto is currently trialling autonomous production drills designed to provide a reliable and repeatable process in blast hole drilling.
According to the Rio Tinto website, the intent of the integrated system is that automated blast hole drill rigs will precisely  position the blast holes, conduct live rock analysis, dictate to the explosives delivery vehicle the correct charge for each hole and provide data supporting three dimensional mapping systems to provide detailed imaging of each deposit. A number of critical system components have already been successfully tested in  Rio Tinto operations.

RESOURCE ASSESSMENT PROCESS
Information gathered in the resource assessment process can assist greatly in the establishment of a long-term workable design for a quarry in terms of the resource size, the optimum quarry design, potential geotechnical issues and the product type and quality.

Ideally, the resource assessment process involves the following integrated technologies:

? An on-board GPS on the drill rig for placement of designed exploration holes.
? On-board logging of rock types and rock properties intersected through MWD capabilities which can derive rock types (including faults and dykes) after calibration, measure drill penetration rate, torque, fracture spacing and other parameters.
? The ability to directly download the data to a three-dimensional resource model which can be updated during the production drilling process as rock types and discontinuities are intersected.

Maximising the amount of data available during the resource assessment process is critical to the design process as changing the design can be costly and affect production output once operations are established. Typical mistakes that can be made through inadequate resource assessment are:

? Locating the infrastructure on top of the resource.
? Inadequate matching of the quarried product to the potential market.
? Not using geotechnical information to assess the optimum orientation of benches.
? Failure to assess geotechnical features which may affect quarry stability in the future.

ESTABLISHING QUARRY  DESIGN PARAMETERS
This step is often overlooked in the quarry design process. Table 1 shows a list of typical design parameters for consideration in the design of a new or existing quarry. In some cases the design parameters may need to be changed, eg the use of smaller height benches in unstable areas or a change in the batter angle in weathered areas. The design parameters should be continually upgraded as changes in the material type, stress and other parameters are encountered in the quarry extraction process.

Outside the technical design parameters, there are a number of other influences that will affect the future use of technology in design. These include the shortage of skilled operators and maintenance personnel, the reduced complexity of modern control systems and the comparative long term cost of current versus automated systems.

The introduction of CANBUS electronic operating systems into modern drill rigs has allowed additional factory components as well as aftermarket components to be easily integrated with the operating system. The system also allows easy access to the database via a website which allows maintenance personnel to check the status of the machine.

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AUTOMATED DRILL AND BLAST
Automated drilling and blasting systems involve autonomous drills which can receive the full blast design and drill hole location via the on-board computer. All drilling data can be sent back to the drilling rig where any redrills can be controlled by the co-ordinator who can view the operations using a remote camera and switch to remote operator mode.

 The drill can directly download resource data to the mine design so that the resource model can be continuously upgraded. The blasting process, using software that is fully integrated with the drilling process, can obtain information on rock types, location of major faults, dykes, fractures, etc and involves an autonomous charging unit which can:

? Clean the holes and report on their condition.
? Install primers and electronic delays and charge the holes with bulk explosives with a variable powder factor in accordance with the ground conditions as provided by the drill.
? Insert the stemming and hook up the system for blasting.

The introduction of autonomous drilling and blasting will be a staged process, initially with the phasing in of automated drills (as already used in underground mining), followed by autonomous drilling with a similar approach to the blasting process.

A pending technology breakthrough is the measurement of hole through the drill string. It is unlikely that the shot-firer will be made redundant in the near future.

CRUSHING, SCREENING AND CONVEYING PROCESS
The use of mobile crushing and screening has become more commonplace in the quarrying industry, particularly with large multi-product operations ranging from roadbase to recycled concrete.

Mobile systems allow operations to be carried in addition to the normal crushing and screening operations for such activities as working in remote areas within a quarry.  They are also suitable for campaign operations and the blending of products meet particular product specifications.

Generally the operating cost of mobile crushing and screening equipment is higher than fixed plant due to:

? The power being direct or from a hydraulic motor or electric power from a generating set for which the cost of power generation is relatively high.
? Higher wear in the componentry and less robustness.
? The double handling of material, depending on the sophistication of the mobile equipment.
The authors are of the opinion that mobile crushing, screening and in-pit conveying systems are yet to be fully developed in Australia in order for quarries to fully  benefit from their operation. The potential benefits include:
? Reduced labour requirements due to multiple equipment operation by one person, eg the excavator or loader operator.
? Reduced energy requirements for transport, particularly where mobile conveyors replace conventional quarry trucks for material transport.
? Increased flexibility of operations, particularly where the quarry material is variable.
The introduction of a fully mobile crushing and screening system to a quarry does require major changes in the quarry design and operation. These can include:
? Modifying the extraction schedule to  allow for long and wide working benches to allow sufficient room for mobile crushing and screening activities and stockpiling to take place.
? Designing quarry haul road gradients to allow road transport trucks directly on to the benches for direct loading from stockpiles. Alternatively, mobile conveying systems can be used to transport the product from the crushing area within an excavation up and over the quarry benches to the surface product storage areas.
? The development of sophisticated on-board software that will allow autonomous operation as well as data feedback on equipment performance to the maintenance personnel who can ?log in?.

Mobile conveying can also incorporate a radial stacker for use in stockpile building. According to Mobile Conveying Services Pty Ltd, Australian importers of innovative  Superior Industries conveyor systems from the United States, the advantages of radial stackers are as follows:
? The potential to reduce dust generated from the stockpiling process by minimising the chute height.
? The ability to stockpile material on the next bench up in the quarry.
? The ability to greatly reduce segregation in the stockpile by layering the material.
? Building a much larger stockpile due to slew and telescopic capabilities.
? They can be changed to directly load trucks if needed, reducing double handling.
Groundline conveyors are essential for any mobile processing system where the extraction area is a distance from the stockpiling area.  A portable groundline conveyor has the following advantages/disadvantages compared to a fixed system:
? It is highly maneouvrable with quick set-up and tear-down times.
? It can be integrated to run up existing haul roads.
? It requires a relatively flat profile and stable ground conditions.

SOFTWARE USED IN THE QUARRYING INDUSTRY
Most software in the quarrying industry is sourced from the mining industry. Typical available software uses in design, operations and data collection include design functions, operating functions, maintenance functions and automatic/autonomous operations.

Design functions
Resource estimation (Deswik, SURPAC, Vulcan, Micromine), Quarry design (Deswik, SURPAC, Vulcan), Scheduling (Deswik, Mine2-4D), Haulage (Deswik,Talpac), Crush and screen design (Aggflow, Sandvik).

Operating functions
Drill and blast design (SURPAC, ShotPlus), Drilling management (Sandvik TIM3D, Atlas Copco RCS), Product sizing analysis (WipFrag), Machine location/proximity/tracking (GPS-based), Performance monitoring (Pitram), Maintenance functions, Equipment maintenance (CMMS), Diagnosis via remote GSM access, Remote reprogramming and updating on board, Providing performance summaries in IREDES format, Collecting cost data.

Automatic/Autonomous Operation
Caterpillar MineStar, Komatsu FrontRunner (Codelco, West Angelas), Atlas Copco (RCS), Sandvik (AutoMine).

INTEGRATING TECHNOLOGIES  FOR DESIGN
It is important that the software systems that are used in the various processes of quarry operations can be easily integrated. Typical software systems and requirements include:

? The resource modelling and quarry  design tools.
? Geotechnical modelling that is integrated with the quarry design.
? Blast design and fragmentation assessment that is integrated with the quarry design software and the data from drilling, in particular major faults and dykes.
? On-board GIS software that can track mobile equipment (either autonomously or by an operator) so that its location matches the design location.
? Equipment monitoring and performance.
One of the reasons for the lack of integration of software systems is the innate competitiveness of the suppliers of equipment and the software systems themselves.
Figure 1 shows a typical integrated software arrangement from resource drilling to blasting using the Atlas Copco MWD concept (Ghosh, 2010).

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CAUTIOUS CHANGES
Technology changes in the quarry industry are generally treated  with caution, particularly in terms of their robustness, cost and simplicity. Recent developments in GPS-based machine positioning and location monitoring, automation and autonomous operation as used in the mining industry are now finding their way into the quarrying industry.

Mobile crushing, screening and conveying systems are replacing fixed infrastructure and conventional trucking systems in certain quarry scenarios. All these technology changes influence how we design quarries but the most important input parameters are those that make up the rock mass that we are extracting – a detailed knowledge of these is the basic essential for a well designed quarry.

Carl Morandy is a mining engineer for consulting mining engineers Ausrocks Pty Ltd. Alan Robertson is the director of Ausrocks Pty Ltd.

References and further reading
Ghosh R, 2010. Optimisation of quarry drill and blast ? The Measure While Drilling (MWD) approach. University of Queensland thesis, Brisbane.