Evolution law and control technology of surrounding rock for weak and broken coal roadway with large cross section

With the increase of mining depth and the cross section size of roadway,the soft and crushing degree of roadway surrounding rock becomes serious,and the risk of roadway roof caving increases as well,which make the sup- port and maintenance of big cross section coal roadway become difficult. Based on the surrounding rock loose circle test and analysis,the deformation and failure characteristics of weak and broken coal roadway with large cross section were revealed. Roadway deformation characteristics,the evolutionary law of plastic zone and the characteristics of sur- rounding rock stress were simulated by FLAC3D under different mining roadway layouts,mining thicknesses,the height- width ratios of roadway and the coefficients of lateral earth pressure. With the work above,the basis for the roadway layout optimization,and the selection of reasonable support pattern and parameters were provided. According to the characteristics of deformation and failure and the difficulties in supporting the roadway,the “ three anchor” combination supporting scheme was put forward,i. e. ,bolting with wire mesh and shotcreting as the first step support,the high prestressed anchor and bolting-grouting as the second step support. Using numerical simulation analysis and similar material model test,the rationality of the scheme and the effect of surrounding rock control were verified,and the un- derground industrial tests were carried out. The result of monitoring shows that the roadway large deformation and bot- tom drum can be effectively controlled with the “three anchor” combined supporting technology,and the stability and safety of coal roadway surrounding rock and supporting structure can be ensured. It is an effective control technology for surrounding rock in coal roadway.