This research has been conducted to investigate the influence of mined cavities on a tunnel to be constructed around a coal mine. The location and dimension of cavities were supposed by analyzing synthetically geological structures and condition of coal beds as well as gangway map since there does not exist any map describing mined cavities. Detailed geological and geophysical surveys have also been carried out for the purpose of understanding the geological structure and rock mass conditions. The two dimensional analysis with FLAC has been performed on the geological sections reconstructed from the obtained information and the effects of mined cavities on the tunnel have been assessed.