There remains debate within the literature and amongst practitioners of caving methods as to the effect upon draw zone geometry when multiple drawpoints are drawn concurrently and the effect of the height of draw when a single drawpoint is drawn in isolation. One hypothesis concludes that the area of influence of a single draw point increases whilst another assumes no change from that of isolated draw. Additionally, the isolated draw zones have been thought to reach a maximum value at a critical height of draw.

The largest 3D physical model ever constructed, using gravel as the model media, was used to further investigate both isolated and interactive draw mechanisms as part of the ICS2 Project. In this model, both extraction zone and movement zone geometries were simultaneously measured in a 3D environment for the first time. To date, only a maximum of two draw bells with four draw points have been modelled to a scaled height of only 100 m. These model results for isolated draw have indicated so far that the extraction zones continue to linearly increase within the tested height of draw. Additionally, no growth in extraction zone horizontal width using interactive draw was noted when up to 4 drawpoints were drawn interactively. However, these results cannot be considered conclusive as numerical modelling and sand model experiments have indicated that to fully test interactive draw necessitates many more drawpoints and a higher height of draw.

In the first year of this project, the effect of drawing multiple drawpoints on the extraction envelopes for more extensive draw areas and heights of draw will be investigated. This will necessitate the drawing of a scaled area of influence of up to 30.000 m2 for a block/panel caving geometry as well as a maximum draw height of up to 330 m. Practical achievement of these conditions, using the same model frame, requires a reduction in scale from the current 1:30 to 1:100 geometric scale. Additionally, the geometry of the extraction zone at a height of draw of 330 m for a single drawpoint will be evaluated. Indications based upon Model Theory are that the model results will still be able to be directly scaled to the full scale at this reduced model scale.

Contact Information
Isles Road, Indooroopilly, Qld Australia 4068
Phone:+61 7 3365 5888
Fax:    +61 7 3365 5999
Email: jkmrc@uq.edu.au