The Evolution Of Geological Models As An Aid To Geotechnical Stability Analysis, Latrobe Valley

Lignite Mining in the Latrobe Valley commenced in the late 19th Century (Drucker, 1984) and three world scale large open pits continue to operate today. Extensive coal exploration, hydrogeological and geotechnical investigation drilling for over a century, enabled the establishment of desktop geological models. Up until the 1980s these models required extensive manual input and updates were onerous. Due to the extensive data available, as well as a team of State Electricity Commission of Victoria (SECV) geologists, the models were considered reliable and carried a reasonable degree of accuracy, including in areas of geotechnical stability interest.

To facilitate potential expansions in the use of lignite, in 2002 a government led initiative resulted in the creation of the digital Latrobe Valley Regional Coal model (Jansen et. al., 2003). This model relied on data from some 8,000 drillholes including the SECV’s stratigraphic interpretations and coal quality results. This model has since grown in extent to cover the Stradbroke area (in 2008) and the Moe Swamp Basin and Seaspray Depression (2011). Of note is the coarse scale of these models with respect to the lignite seams which required seam definition rules to define the extent of the seams which tend to split at basin margins.

Each of the operating mines has a more sophisticated subset of the model and include hydrogeological and additional structural detail. Such detail is required in areas both within the operational and non-operational areas of the mine, where geotechnical stability carries significant importance. The models allow rapid sectional work providing slope angles of coal seams for geotechnical studies as required. Such studies are valuable in the planning for various conceptual mining and infrastructure projects.