Determination of three-level energy absorbing support parameters in rockburst roadway based on energy calculation

The engineering treatment of rockburst in coal mines mainly reflects in the two aspects of“prevention”before the bursting start-up and "stop" after the rockburst initiation. Furtherly,involving the rockburst type and energy characteristics for parameters design of the energy absorbing support is important to effectively stop bursting and weaken the bursting damage degree. For quantitative design of energy absorbing support parameters in rockburst roadways,the main energy releasing bodies and failure characteristics of different type rockburst were analyzed and selection principles of three-level energy absorbing support in burst-prone roadway were proposed. Based on the energy conservation,the determination method of three-level energy absorbing support parameters was given,considering the energy level of rockburst release,the failure characteristics of surrounding rock and the mechanical characteristics of support equipment. The results show that,the main energy-releasing body of coal compression type rockburst is coal mass,and its released energy is not more than 106 J; the main energy-releasing body of roof fracture type rockburst is roof and floor,and its released energy is no less than 106 J; the main energy-releasing body of fault dislocation type rockburst is fault structure,and the released energy is more than 107 J. After the occurrence of different types of rock burst,the surrounding rock of roadway shows different degrees of vibration damage. Therefore,some principles should be followed in design of energy absorbing support,involving rockburst energy classification prevention,active support priority of bolt and cables,active-passive combined and overall-section support,overall stability of roadway support structure and economic applicability. Hierarchical progressive method should be used to quantitatively determine the burst-resistance support parameters,successively including the support parameters of energy absorbing anchor cable,U/O-shed and hydraulic support. When the support spacing of energy absorbing anchor cable is less than 0.8 m,design degree is upgraded to two-level energy absorbing calculation; when the row spacing of energy absorbing U/O-shed is less than 0.6 m,corresponding degree is upgraded to three-level. The field practice shows that the parameter design method of three-level energy absorbing support based is reliable and the effect of burst-resistance of roadway is remarkable.