Abstract:
The in-situ mechanical properties of Huntly coal are investigated. Laboratory tests on core specimens and small scale in-situ pressuremeter testing are used to determine elastic properties and failure criteria of the coal and coal measure rocks. The in-situ stress field that exists in the Waikato basin and in particular in the Test Panel of the No 1 West Mine is determined. An instrument is developed especially to measure in-situ stress in coal.
To check in-situ behaviour of the coal seam, a full scale underground roadway is excavated in the Test Panel. Stress changes and deformations are monitored from nearby drives allowing all the changes to be observed, even those that are normally missed because they occur ahead of excavation.
Using elastic properties and in-situ stresses determined from small scale tests, the roadway excavation is mathematically modelled using the finite element technique. Stress changes and deformations thus calculated are compared to those measured in the full scale test.
With evidence gained in the Test Panel investigation, general observations of tunnel behaviour elsewhere in the mine are investigated. Some problems that have beset the mine are identified and solutions are found.
