The Mt Whaleback orebody is in a complex geological regime. A good
understanding of geological structure is essential during the design and
implementation stages. The amount of information on the rock-mass
condition available at the design stage is considerably limited. It is
essential to validate the rock-mass properties used in the design during
implementation. It is important to achieve integrity of the final pit wall
during development and to maintain the integrity until the end of its
designed life for safe and economical extraction of ore. The original geological model is updated by way of on-going detailed
geological face mapping. Original design is reassessed and is modified
based on any significant variations to the previously evaluated
geotechnical conditions. Information gathered during design
implementation provide tools for effective management of the pit walls. Controlled blasting techniques are employed in the final limits blasting.
Presplit blasting is used in most limits blasts. Presplit helps to maintain
the integrity of the wall by venting excessive gases from the limits blast.
This helps to reduce bedding dilation by gas penetration. Also, it helps to
define the design batter for the operators for final batter trimming. Pyritic
shale needs special attention during blasting due to its reacting nature.
Cablebolting is applied in selective areas to secure small-scale potential
instabilities. During the development phase, pit wall monitoring
instruments are installed. These instruments are used to monitor the
performance of the wall during and after excavation of the slope.