Use of Numerical Tools to Evaluate Site Specific Issues Using a Mine Scale Model

Khanal, M. (CSIRO Earth Science and Resource Engineering) | Adhikary, D. (CSIRO Earth Science and Resource Engineering) | Balusu, R. (CSIRO Earth Science and Resource Engineering)


Reliable methods must be used to perform a realistic assessment of mine roof support requirement and address the geotechnical risks associated with longwall mining. Dependable tools provide a safe working environment, increased production, efficient management of resources and reduce environmental impacts of mining. Although various methods, for example, analytical, experimental and empirical are being adopted in mining, in recent days numerical tools are becoming popular due to the advancement in computer hardware and numerical methods. Empirical rules based on past experiences do provide a general guide, however due to the heterogeneous nature of mine geology (i.e. none of the mine sites are identical), numerical simulations of mine site specific conditions would lend better insights into some underlying issues. The paper highlights the use of a continuum mechanics based tool in coal mining with a mine scale model. The continuum modeling can provide close to accurate stress fields and deformation. The paper describes the use of existing mine data to calibrate and validate the model parameters, which then are used to assess geotechnical issues related with installing a new high capacity longwall mine at the mine site. A variety of parameters, for example, chock convergences, caveability of top coal and overlying sandstones have been estimated.


The paper describes numerical simulations of longwall mining. Geotechnical specifications depend on the geological information of mines, so none of the mines can be considered to be identical and the experience from any previous mine is not completely portable. In some respect the past experience can be used as a preface step in planning the new mine. The detailed investigation of site specific issues, for example chock capacity requirement, strata caving behaviour, roof displacement and top coal caveability (in case of longwall top coal caving, LTCC) should be evaluated appropriately in order to gain confidence in mine design. The roof support system is critical in successful mining operations [1]. The requirement and selection of roof support systems depend on site specific geotechnical conditions [2], for example nature and strength of overlaying strata, strength, orientation and height of mining, panel geometry and layouts, and the capital cost. These factors, which may vary in various mine sites, necessitate selecting an optimum roof support system. So the understanding of response of support capacity under local geotechnical conditions is vital for a site specific mining environment. Poor ground condition combined with poor choice of support may cause face instability [3,4]. Understanding the causes of face instability specifically determining whether they were simply the result of insufficient support capacity or whether the deployment of better mining techniques or more appropriate support could have avoided the events is important. Support design is based primarily on the replacement of the extracted coal with mechanized support capable of controlling the deformation in the immediate roof, the design being of sufficient capacity to allow effective mechanized extraction at the desired production rate. An optimum capacity of roof support systems provides safe as well as efficient mining operations [4].