Prediction of the stresses around main and tail gates during top coal caving by 3D numerical analysis

• 3D global model of underground coal mine using the LTCC was constructed by FLAC3D.
• The mining induced stresses around main and tail gates were predicted.
• Regarding mining induced stresses two stages are determined for each roadway.
• The magnitude of mining induced stresses in second stage occurring due to the advancing mining face is larger than the first stage.
• Mining induced stresses around gateway may threefold the insitu vertical stress.
• The predicted and presented stresses will be used in the detailed stability analysis of roadways.

The objective of this paper is to predict the stresses around the tail and main gates of Soma Eynez underground coal mine, located in Western part of Turkey. In the studied mine, the magnitude and the direction of stresses around the gateways frequently change due to a planned mining method, which is a combination of a fully mechanized traditional longwall and longwall top coal caving (LTCC) methods. In the mine, a 30–35 m thick coal seam is going to be produced by three slices. The upper slice will be produced by fully mechanized traditional longwall mining, whereas the remaining two slices will be exploited by the LTCC method. Although both traditional longwall and LTCC methods are widely used around the world, a mine using a combination of both is rare. This unique application presents special challenges for designing a support system, as the magnitude and the orientation of the stresses around the gateways change frequently. Due to the planned mining method, empirical and analytical methods cannot be used to assess the stresses around the gateways. Therefore, a three-dimensional finite difference technique is selected for mine scale stress analysis, and the results presented will be used in further stability analysis of tail and main gates.