Design and Design Review
Examples of Design in Action...
Arygle Diamond Mine Drawbell and Undercut Design
Drawbell drill pattern designs modified for single shot firing. This change was made in conjunction with drill accuracy controls leading to a 50% reduction in redrill meters.
Undercut redesign to reduce sensitivity to adverse ground conditions…
… resulted in 50% increase in undercut rate with corresponding reduction in rework.
Oly Tolgoi Drawbell and Undercut Design
Drawbell and Undercut design for Rio Tinto’s OT Operation.
Olympic Dam Slot Re-Design
Re-design of the OD slots to reduce sensitivity to drill deviation. This required the development of statistical models to assess the effect of drill deviation when firing raises and slots. The outcome was a widened slot design that delivered an 80% reduction in slot bridges.
The effect of drill deviation in raises and slots was modelled using monte-carlo analysis. This enabled a range of designs to be assessed for sensitivity to drill error.
Coal Loss and Dilution
Between 2007 and 2010 engaged by BMA to address Coal Loss and Dilution as part of the ‘Last Drop’ project. Many of the project elements were focussed on the delivery of design and variance between the design and the as-built.
Presplit Review
Modifications to presplit designs based on standard tensile failure models resulted in significant improvements to presplit performance. Associated benefits including increased bucket life were identified.
Box Cut Re-Design
Box Cut re-design driven by management of relief resulted in increased blast performance at overall reduction in cost and powder factor.
Video
Somilo Slot
Re-design of production slots at Somilo Gold in West Africa. Resulting in elimination of persistent slot bridges.
Cast to Standup Transitions
Modification to design standards for both drilling and loading to achieve transition from cast to standup blasting for strips with highwalls over 50m.
Interactive Timing
Interactive timing is a concept where independent holes are fired with reduced time separation so that the material around the holes is impacted by energy from multiple holes.
Interactive timing is not realistic for dependent holes owing to the requirement for burden relief.
Interactive timing is relevant for holes within a maximum distance of around 1.5 burdens:
The delay between holes is not before the compression wave reaches the free face and before first movement. In the following example interactive timing is between 1.5 and 6 milliseconds.
Note the distance between holes (spacing) the burden and the P wave velocity all influence interactive timing. Therefore there is a not a single ‘right’ delay between or within a pattern but rather a range of delays to meet the requirements of interactive timing.
When determining timing for interactive timing the proximity of interactive holes is a limitation.
Owing to this firing is limited to row by row, Vee or Vee 1 only:
To setup interactive timing using a timing contour for electronic initiation it is a simple matter to align the contour to the true spacing and then rotate by the required angle:
In the following example the interactive delay of 4 milliseconds is achieved with a contour line rotated 1.07 degrees.
The application of interactive timing determines the true burden and spacing. These should be considered in drill pattern design.
Rather than blindly aligning the rows to the available free face or blast perimeter consideration should be given to aligning the rows (spacing) perpendicular to the expected direction of movement.
