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 regions at the working face design stage.In this situation,it is urgent to develop new methods of rockburst risk early evaluation and timely warning characterized by much more scientific,accurate,quantitative and easily to operate for technical 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 analyzed 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 authors established the rockburst risk lever system which has been proved to be more accurate,more conducive and beneficial to guide a safe production by field application.%冲击动力灾害是关乎矿井能否安全稳定生产的主要因素,目前越来越多的矿井需要在采掘工作面设计阶段确定冲击危险等级与区域,迫切需要发展科学、精确、定量、便于技术人员操作的冲击危险早期评价预警方法.为了解决冲击显现无法用现有强度准则进行表述、不同应力无法标量叠加的问题,提出了冲击危险评价的相对应力集中系数叠加法,将某一待分析区域内影响冲击矿压发生的某因素引起的最大主应力与自重应力的比值,称为相对应力集中系数分量,各分量的乘积为该区域的相对应力集中系数.将影响冲击矿压的因素从载荷特性上分为静载荷和动载荷,从对应力影响效果上分为增压型与减压型,给出了影响冲击的主要动载因素,以及相对应力集中系数计算方法.发生过冲击矿压的矿井利用冲击区域的总相对应力集中系数作为临界指标,未发生冲击的矿井利用临界应力与自重应力的比值作为临界值,根据相对应力叠加系数与临界值的比值对冲击危险等级进行了划分.现场应用表明,相对应力集中系数叠加法与监测冲击危险区域与等级具有较高一致性.
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