Strength calculation method of three-level energy absorption support in rockburst roadways for coal mines

To develope a quantitative design method for anti-impact and energy absorption support in rockburst roadway,the strength calculation method of anti-impact and energy absorption support was studied,considering static and dynamic stress environment of surrounding rock and structural characteristics of rockburst roadway. The results showed that the surrounding rock in rockburst roadways forms a multi-layer ring structure with support layer,anchorage layer,pressure-relief layer and elastic layer due to the double existence of support and pressure relief engineerings. Further,the surrounding rock with multi-layer structure behaves typical gradient physical properties in the radial direction of the roadway. Using quasi-static method,a mechanical model of the surrounding rock with gradient structure in rockburst roadway was established,by superposing the far-field impact loading and the surrounding rock static loading,simplifying the anchor bolt in the anchorage layer,and weakening the mechanical parameters of the coal-rock mass in the pressure-relief layer. And then the force analysis between the contact surfaces of multi-layer ring in the gradient surrounding rock structure was carried out and calculated the stress on contact surface of multi-layer ring structures. The reduction of impact loading on the support layer and the enhance of rockburst-resistant level of the support layer in the roadway can be achieved by weakening the mechanical properties of coal and rock in the pressure-relief layer,increasing the structural size of the pressure-relief layer and increasing the support strength of the anchorage layer. The impact damage level coefficient was introduced to establish the relationship between the energy absorption support strength and rockburst level. Finally,strength calculation method of three-level burst-resistant support for impact mines was proposed. The quantitative design of anti-impact and energy absorption support parameters for rockburst roadway was realized. Combined with the engineering practice of some mine,it was verified that the three-level energy absorption and burst-resistant support parameters of “ bolt ( cable) +36U retractable support+hydraulic lifting shed and anti-impact hydraulic support” adopted by the mine can resist the rockburst of level 2 at the maximum( equivalent to the shock source releasing energy 10……8J and 100 m away from the roadway).