Best practice blasting in close proximity to infrastructure

The successful delivery of a complex drill and blast operation at an iron ore project in Western Australia’s Pilbara region has built a blueprint for best practice blasting in close proximity to infrastructure.  

The project comprises a number of new deposits that are being developed to sustain production across the operations.

This requires working in and around the existing site facilities with some blast areas just 30 metres from major infrastructure.

This required blasts to comply with strict vibration and flyrock limitations while adhering to a tight schedule and blast window to minimise delays and disruptions to the operations.

A progressive methodology

To meet the deliverables of the operation, drill and blast contractor JSW Australia applied a progressive and detailed methodology to the blast design, execution and evaluation.

The process encompassed:

  • Advanced 3D modelling and design of the areas
  • Advanced vibration prediction algorithms to predict vibration for every individual hole based on its specific charge weight and distance
  • Detailed timing initiation plans including focus around vibration frequency control
  • Utilisation of electronic detonators to allow one millisecond timing interval control and advanced single hole firing capability.

The process included the development of site-specific vibration laws based on collected data and analysis of vibration PPV and waveforms.

James Chomley, JSW general manager said: “Generally it is acceptable that you would just use the maximum instantaneous charge (MIC) hole and the distance from this to the infrastructure to predict vibration.

“Our methodology is far more detailed and provides greater accuracy by running vibration predictions on every hole on every blast rather than just the once for each blast.”

Industry-leading quality assurance comprised an iterative program and monitoring procedure to continuously improve blast outcomes including vibration results.

“The constant feedback cycle resulted in improved vibration frequencies and minimised the potential of damaging frequencies,” Chomley said.

Successful delivery

This precision allowed all blasts to be successfully undertaken with no flyrock ejection, and no damage or delay to operations.

A total of 120 blasts all subjected to JSW’s quality and HSET management system resulted in total material movement of circa 750,000 bank cubic metres.

JSW continues to deploy the approach, applying ongoing evaluation and improvements at all its applicable drill and blast projects.

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