基于动静应力分析的复杂工作面冲击危险评价

Rock burst risk evaluation based on dynamic-static stress analysis in complex working face

为在回采前定量评价复杂条件工作面冲击危险等级及划分冲击危险区域,基于冲击矿压发生的动静叠加诱冲原理,以济宁三号煤矿复杂条件工作面为工程背景,提出了基于动静应力分析的冲击危险评价方法。实验室试验研究表明,煤体动力破坏的临界应力与煤的单轴抗压强度密切相关,根据煤体单轴抗压强度,确定了济宁三号煤矿复杂工作面冲击临界应力为70MPa。采用FLAC3D数值软件,研究了工作面原岩应力与采动支承压力分布规律,得到了静载应力分布曲线。探讨了工作面过断层期间的应力演化规律,根据断层至工作面的距离,将采动作用下断层附近支承压力对冲击影响程度分为4级,即小于10 m时为塑性变形区,10~20m为冲击弹性区,20~50m为应力叠加区,大于50m为原始应力区。采用理论分析,计算了坚硬顶板破断来压的能量释放规律,工作面基本顶破断步距在50m时,释放能量达到105J,对应动载应力为10MPa。基于动静载应力水平,给出了冲击危险等级评价与划分标准,将冲击危险性分为4级,动静载最大叠加应力小于50 MPa为无冲击危险;50~70MPa为弱冲击危险;70~105MPa为中等冲击危险,大于105 MPa为强冲击危险。对123下04工作面冲击危险进行了评价与分区,与现场微震监测结果具有较高的一致性,为工作面的安全回采提供了支持。

In order to quantitatively evaluate the rockburst impact hazard level and the division of hazard area before the mining of complex working face,and based on the dynamic and static superposition principle of rockburst,the complex condition working face of Jining No.3 Coal Mine is taken as the engineering background,a rockburst assessment method based on dynamic and static stress analysis was proposed in this paper.Laboratory tests have shown that the critical stress of dynamic failure of coal was closely related to the uniaxial compressive strength.According to the uniaxial compressive strength of coal,the critical impact stress of Jining No.3 Coal Mine was determined to be70 MPa.The FLAC numerical software was used to study the distribution law of the original rock stress and the mining support pressure,and the static load stress distribution curve was obtained.The stress evolution law of the working face during the fault crossing was discussed.According to the distance of the fault from the working face,the influence of the supporting pressure near the fault under the mining activity was divided into 4 grades,that is,the plastic deformation zone(less than 10 m),the impact elastic zone(10~20 m),the stress superposition zone(20 to 50 m),and the original stress zone(more than 50 m).Based on theoretical analysis,the energy release law of hard roof breaking was calculated.When the breakage step distance of the main roof reaches 50 m,the release of energy canreach 105 J and the corresponding dynamic load stress is 10 MPa.Based on the static and dynamic stress level,the rockburst hazard eval-uation criteria are given and the impact risk is divided into 4 levels.No impact risk when the maximum superimposed stress of dynamic and static load is less than50 MPa,weak impact risk at 50 MPa to 70 MPa,medium impact risk at 70 MPa to 105 MPa,and strong impact hazard when the stress is more than 105 MPa.The impact risk of the 123 working face was evaluated and divided,which was consistent with the results of the on-site microseismic monitoring and this provides support for the safe mining of the working face.