New method of rockburst risk assessment using relative stress concentration factor superposition

Dynamic disasters are the main factors relating to the safe and stable coal mine production. Therefore,more and more collieries need to carry out assessments for determining both the rockburst danger lever and prevention re- gions at the working face design stage. In this situation,it is urgent to develop new methods of rockburst risk early eval- uation and timely warning characterized by much more scientific,accurate,quantitative and easily to operate for techni- cal personnel. In order to address the problem that rockburst phenomenon cannot be expressed by the existing strength criterion as well as different stress cannot be assessed by scalar superposition,the authors put forward a new method of rockburst risk assessment using relative stress concentration factor superposition. The ration that divided by the maximum principal stress induced by a certain influencing factor of rockburst and the gravity stress in the area to be ana- lyzed is defined as relative stress concentration factor component,and then the product of each component is named as relative stress concentration factor of the region. In this paper,the stresses relating to rockburst are classified into static and dynamic loads based on the strain rate character,and into decompression and supercharge based on the effects on stress state. The main factors causing dynamic loads and the relative stress concentration factor calculation method are analyzed in this study. The total relative stress concentration factor is used as the critical indicators in the coal mines where rockburst had been occurred while the ration of critical stress and weight stress as the threshold in the areas where rockburst never happened. Using the specific value of relative stress concentration factor and threshold,the au- thors established the rockburst risk lever system which has been proved to be more accurate,more conducive and bene- ficial to guide a safe production by field application.