Damages to the roadway tunnels in the coal mining area of Hebi, P.R. China: proposals to minimise damages and numerical analysis

The influence of a coal mining operation on the roadways constructed in the underlying rock strata is generally well known. In a joint research project between CCMRI (Beijing) and the Technical University Graz (Austria) the frequent damage to the roadways in the Hebi mining area resulting from the longwall mining operation of the overlying coal-seam were investigated. The likely cause of the damage was established and proposals were made to improve the tunnel performance by a modification of the cross-sectional geometry and of the driving operation of the tunnels whereby the principles of the New Austrian Tunnelling Method (NATM) were employed. The aim was to minimise or to avoid the damages caused by the mining operation and thus reduce the high cost of constant repairs. A well instrumented test section of the modified tunnel was constructed and its performance during the ensuing coal extraction was monitored. The paper describes the initial investigations, the NATM proposals, as well as a brief description and the interpretation of a FEM analysis made in this connection. 6 refs., 11 figs., 1 tab