| Popis: |
Two coal mining companies proposed to undertake, respectively, longwall mining beneath an existing tailings dam, and open cut mining adjacent to it. 3D numerical stress analyses, using program FLAC3D, were performed to examine this system, as one component of meeting regulatory requirements. Rock cohesions and tensile strengths from earlier 2D modelling had to be reduced by a factor of five to produce modelled surface subsidence comparable with that observed over previous longwall panels. Those properties were then used in the final models, resulting in predicted factors of safety not less than 1.80 for the open cut walls and for the tailings dam. The longwall panels have since been mined, and the open cut is close to completion, without incident. |
