Infra-red thermography of loose hangingwalls

This project is the continuation of GAP706 “Pre-feasibility investigation of infrared thermography for the identification of loose hangingwall and impending falls of ground”. The main concept behind the infrared thermography method is that with an exposed hangingwall surface area, loose sections of ventilated rock should have a lower temperature than solid sections of ventilated rock because the former acts like cooling fins. The temperature gradient between loose and solid rock depends on the thermal conductivity of the rock, the ventilation conditions, the looseness of the rock and, to a lesser extent, the type of rock and age of mining. Such a gradient could be anything from a tenth of a degree to a few degrees Centigrade.
Underground tests have been conducted at Anglo Platinum Townlands platinum mine and Gold Fields Driefontein 5 shaft gold mine. The obtained results demonstrate that the method of IR thermography for identification of loose hangingwall is only applicable for primary roof-bolt installation during the first 24 hours after a blast.
The concept of a mine worthy IR thermometer is proposed. It is recommended that the MX4 IR thermometer be modified in accordance with the proposed concept. These devices should be provided to a couple of development teams for practical evaluation. It is expected that the device will provide better identification of loose hanging walls, which are difficult to detect visually. The evaluation results, as obtained from the development teams, should facilitate a final decision on the applicability of the IR thermography for the South African mining industry.
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