Study on the width of plastic zone in coal rib with containing gas based on Mohr-Coulomb yield criterion

On the basis of the theory of instability of coal seam developed by Lippmann, the model of translatory coal burst in coal seam, which is covered with rock strata for both coal roof and floor, is derived by using the Mohr-Coulomb yield criterion with considering effects of gas pressure and the support resistance. The analytical formulas of coal seam stresses before instability, plastic zone width and disturbance zone length are also derived. Combining with the production in two mining fields, the curves of coal seam stress distribution are obtained which proves the validity of the model. Based on the model of translatory coal burst, the factors affecting the width of the plastic zone are analyzed and discussed. The results show that: the plastic zone width is less affected by the roadway width but increases with the height of roadway; the great ground stress and gas pressure could induce the greater the length of the outburst coal seam; The risk of coal burst and instability of coal seam can be reduced by strengthening coal strength and optimizing the supporting method.