Calculation method of rock burst resistance grade of O-shaped shed support

The O-shaped shed support has good surface protection,and is often used to control the deformation and damage of surrounding rock fracture area in the rock burst roadway. However,the design of O-shaped shed support pa- rameters mainly depends on the empirical method,which lacks the corresponding theoretical basis and scientific calcu- lation method. Based on the working principle of O-shaped shed support,the characteristic curve and the maximum support resistance of O-shaped shed support are obtained. It is found that the maximum support resistance of O-shaped shed support is closely related to the type of U-shaped steel and the filling parameters behind the wall. Through the theoretical analysis on the propagation law of the shock stress wave in the coal and rock medium,it is found that the magnitude of the impact force of the rock burst on the roadway support mainly depends on the maximum acceleration of the surrounding rock mass near the roadway,so a new index of evaluating the grade of rock burst,i. e. ,the failure co- efficient Kg of rock burst,is proposed. It is used for the design of the supporting parameters of the O-shaped shed in the roadway under the impact of ground pressure. The relationship between the impact load of surrounding rock and the supporting resistance of the O-shaped shed,the vibration energy and the failure coefficient of the impact ground pres- sure are calculated by using the multi-layer structure method,and then the calculation formula of the level of the im- pact ground pressure that the O-shaped shed can resist is obtained. It is found that the grade of rock burst resistance of O-shaped shed support is mainly affected by the magnitude of rock burst energy, the distance between the impact source and the roadway,and the mechanical properties of surrounding rock and coal medium. Through the comparison of field application results,it is found that the grade of resistance to impact the ground pressure of O-shaped shed sup- port after the optimization of design parameters is significantly improved. The optimized O-shaped shed support suc- cessfully resists multiple impact events and avoids the plastic deformation and damage of support,which shows that the calculation method of O-shaped shed support’s resistance to rock burst has a high reliability. Through the calculation, it is found that the common 36U steel O-shaped shed support can resist the impact ground pressure of medium impact. Therefore,for the roadway with strong impact risk,it is necessary to add hydraulic support for compensation support to improve the impact resistance of roadway support.