Managing impacts of open-cut mine blasting

EnviroSuite US general manager, Matt Scholl

EnviroSuite’s Matt Scholl discusses how predictive software has been effective in managing the impacts of blasting activities.

Open-cut mining operations are constantly faced with the challenge of conducting mining blasts that maximise production, but also minimise impacts on their workforce and surrounding areas.

Blasting operators must consider weather conditions such as rainfall, wind and atmospheric mixing, as each can have a significant bearing on the generation of dust and fume clouds and where these might travel, causing adverse impacts.

Wet ground conditions can be particularly problematic where it effects the efficiency of blast detonation.

Moisture, as well as blast product characteristics, blast design and drill and blast operational practices, can result in large brown, orange or reddish plumes when detonated.

These post blast clouds are very noticeable and can cause concerns for residents in nearby communities. Avoiding these plumes is top-of-mind for any mine supervisor or drill and blast superintendent.

Air vibrations caused by blasting are another challenge. Air vibrations occur when pressure or shock waves are propelled into the atmosphere from a detonating charge.

Certain atmospheric conditions may cause these air vibrations to be reflected back down to the ground. This can result in residents close to the mine avoiding impacts of the blast, but others further away may be affected.

If atmospheric conditions are conducive to refractions, this can result in a surge of noise and vibration complaints.

Rule-of-thumb calculations

Traditionally, assessing the best times at which to conduct blasts in an open-cut mine has been done using a combination of operator experience, local knowledge and gut feel.

Armed with forecasts from the Bureau of Meteorology (BoM) or other generic weather forecasting applications and some local observations, blast superintendents have had to make the call on where and when blasting activity is undertaken.

While this approach might work most of the time, fickle weather conditions and sudden changes can mean blasts end up causing large plumes and significant problems for nearby towns – a problem that seems to gather more intense attention with each occurrence.

Blast fume events can also have serious health impacts on the staff working at the mine itself if a plume is unexpectedly blown towards them in a nearby section.

Computerised simulations

A more effective approach is to make use of software tools that can assess conditions and make recommendations of where and when blasts should be conducted.

The tools can use data from a variety of sources to model the size and nature of predicted plumes, thereby allowing mine managers to make informed decisions prior to blasting.

As a first step, the tools can create a detailed three-dimensional map of the mine site. This is used to support models that predict how wind flow might be affected by the local terrain.

The next step is to model local weather conditions and simulate the likely dispersion and area of impact of blast plumes under different conditions throughout the shift.

Data from weather observation satellites and ground-based weather monitoring networks are used to create high resolution model predictions for blast scenarios at the site.

Because these forecasting systems are set up at highly localised resolution the predictions are much more accurate than those provided by the weather forecasting services that are designed to deliver predictions for much wider areas.

Using the custom configured forecasting system for the mine and an easy to use software interface, simulations of blast plume scenarios can be run for every 15-30-minute time slot over the next 72-hour period.

The system provides results that enable drill and blast teams to plan the best times to conduct blasting over the next few days to achieve maximum productivity, reduce downtime for blast activities and ensure that impacts on community and fellow mine workers are avoided.

Practical support

Outputs provided by these software tools can deliver significant benefits to mine operators.

For example, at an open-cut mine in Central Queensland, conditions that evolved during the loading of a blast pattern meant that a blast plume was likely to be unavoidable.

The mine operator used the software tools to determine when the best time would be to ensure the plume remained within the mining lease or at worst case was not blown into a nearby town.

After the blasts had occurred, the mine was visited by mine Inspectors in response to complaints lodged by local community and news reports that a large blast fume cloud had been created.

They called a stop to all mining operations until they could be convinced that the mine had adequate controls around fume management.

Once the inspectors had been shown the system that the mine was using to manage adverse blasting impacts, including multiple simulations that had been assessed prior to a decision to delay the blast for two hours to avoid impacting the town, they were impressed with the site’s ability to accurately predict and manage the path and dispersion of blast plumes, and subsequently lifted the stop work order immediately.

Weather forecasting systems can also be used to assist in operational mine planning. For example, the tools can predict when critical weather conditions are likely to occur, such as a specific amount of rain within a certain timeframe, where these conditions may impact the safe operation of heavy haul trucks using inclined haul roads.

High quality forecast data provides mine operators to plan alternative operating scenarios or make best use of the unavoidable downtime due to weather.

Similarly, wind speed forecasts can assist mine planners to optimise dust control activities, resulting in better use of costly water resources during good conditions or targeted higher-level dust management during unfavourable weather conditions.

Operational improvements

Putting these sophisticated software tools to work at a mine site can deliver significant benefits for operators.

The ability to forecast future weather conditions can ensure the impact of activity on local communities is minimised while productivity in the mine is maximised.

Industry experience shows the predictive tools can assist mine operators to reduce the number of exceeded operating licence conditions or complaints received by local residents by as much as 500 per cent during a 12-month period.

Mine operations can also benefit financially. Operators using the tools report that production levels have increased thanks to the ability to optimise operations with foresight ahead of weather events.

The tools ensure mine owners are also better placed to maintain their social licence to operate. By proactively minimising their impact on local residents, they are seen as being more responsible members of their community.

By taking advantage of modelling and predictive tools, mine operators can be sure they are operating as efficiently as possible at all times while at the same time minimising their impact on their workforce and their surrounding area.

Matt Scholl is vice president of EnviroSuite.

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