This paper presents the results of computer modelling of existing ground movements and those to be expected within the Loy Yang Mine for the new development area using PLAXIS software. Brown coal resources in the Latrobe Valley (Victoria, Australia) are amongst the largest in the world, representing 20 percent of the world's reserves. They have provided most of the fuel for Victoria's electricity generation since the 1920s. Loy Yang Mine, the largest open pit coal mine in Australia, supplies some 31 Mt/annum coal. Open pit excavation results in depressurisation of groundwater, and stress release, of the pit walls leading to ground movement in surrounding area potentially affecting nearby infrastructure. Prediction of this ground movement assists the design and selection of the infrastructure locations in the mine environment. Current survey monitoring data, indicating ground movements of the order of 3 m over the 25 years the mine has been operating, was used to calibrate the PLAXIS model for ground movement analyses. Predictive modelling of ground movements for the future mine development, to a maximum depth of 250 m, indicates estimated horizontal movement of approximately 4.5 m, and 4 m of subsidence near the potential mine crest.
Brown coal resources in the Latrobe Valley (Victoria, Australia) are amongst the largest in the world, representing 20 per cent of the world's reserves. They have provided most of the fuel for Victoria's electricity generation since the 1920's and are the basis for much of the State's industrial development. Loy Yang Mine, the largest open pit coal mine in Australia, supplies some 31 Mt/anum to the adjacent Loy Yang Power 2200 MW and International Mitsui 1000 MW power stations and other industrial customers. Open pit excavation results in depressurisation of groundwater and stress release of the pit slopes leading to ground movement in the surrounding area, affecting nearby mine infrastructure. Prediction of this ground movement assists in the design and selection of the infrastructure located in the mine environment. Current survey monitoring data was used to calibrate the PLAXIS model for prediction of the future ground movements.
The Loy Yang Mine is situated in the Latrobe Valley Depression, with the underlying basement rock generally consisting of Mesozoic sandstones and siltstones. The overlying Tertiary Latrobe Valley Coal Measures consist of the Traralgon Formation and the overlying Morwell and Yallourn Formations. The Morwell Formation consists of the M2C (oldest), M2B, M2A, M1B and the M1A coal seams, which are generally separated by interseam sediments identified by the overlying coal seam. The Yallourn coal seam overlies this formation and is separated from it by the Yallourn interseam (Holdgate 2003). Loy Yang Mine currently excavates the Yallourn, M1A, M1B, M2A and M2B coal seams. The M1B, M2A and M2B interseams consist of silts, sands and clays. Coal joint mapping results indicate that the predominant major joint direction is approximately grid north, the dip is sub-vertical and that 70% to 80% of these joints appear to extend through all the Morwell.