Rippability assessments for the proposed open pit gold min at Globe-Progress, Reefton, New Zealand

There are many methods used to predict the rippability evaluation of a site may be performed by determining the seismic velocity variation within the rock mass. Seismic velocities are used as an estimate of rippability because they are influenced by geological and physical properties of the rock mass. However, a complete rippability evaluation requires rock mass and rock material characterisation as well as data on possible ripping machinery to be used. If rock mass is rated as being very good rock, then ripping may be difficult. Likewise, if the bulldozer is underpowered, its productivity may be too low and the ripping rate will be slow.

Six seismic refraction traverse lines were surveyed at the proposed open pit gold mine at Globe-Progress, near Reefton using a single channel seismograph, then interpreted using the Generalised Reciprocal Method. Combining the seismic velocities found and data on Komatsu’s D575A-2 bulldozer, it is estimated that 85% of the pit is rippable, and a further 7.5% is marginal. This means that 7.5% of the open pit area is unlikely to be rippable. However, further seismic refraction surveys, as well as a complete rock mass classification, need to be done to provide a three-dimensional site model and to clearly identify the rippable, marginal and non-rippable zones.