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近直立煤层冲击危险静动态评价方法研究

Static-dynamic rockburst risk assessment method in near-vertical coal seams

  • 摘要: 现有冲击地压危险评价方法以采掘前揭露的地质条件和开采技术条件为依据,属于静态评价,评价结果与真实情况存在差距,如何与采掘过程中的监测数据相结合得到更加符合实际的评价结果是需要进一步解决的问题。为此,综合地质及开采条件和监测数据,提出了一种冲击地压危险静动态耦合评价方法,并在典型近直立煤层工作面进行了应用。首先,通过改进综合指数法提出工作面采掘前静态评价方法,包括将综合指数法包含的评价指标进行线性归一化得到单指标危险指数,利用层次分析法对各评价指标赋权,通过加权求和分别得到地质因素和开采技术因素确定的危险指数,然后将两个危险指数加权平均得到静态评价危险指数;其次,利用监测数据构建了采掘过程中动态评价方法,包括根据微震和钻孔应力监测特点及其与冲击危险性的关系,构建了微震能量密度和钻孔应力变化率作为动态评价指标,将评价指标线性归一化分别得到震动场评价指数和应力场评价指数,将两者加权平均得到动态评价危险指数;最后,利用加权平均法将静态评价危险指数和动态评价危险指数进行耦合叠加得到耦合评价危险指数,根据该指数来确定危险等级和危险区域。上述方法在乌东煤矿+450B3+6工作面的应用结果显示,静态评价方法在工作面回采前划定4个中等冲击危险区和1个弱冲击危险区,动态评价方法判定工作面回采过程中岩柱侧具有较高冲击危险性,静动态耦合评价将静态评价的部分弱冲击危险区再评价为中等冲击危险区;通过工作面回采过程的支架压力监测数据、数值模拟结果和冲击地压显现事件对评价结果进行了检验,发现静动态耦合评价结果更符合现场实际。研究成果为冲击地压危险评价提供了一种新方法和新思路。

     

    Abstract: The existing rockburst risk assessment methods generally belong to static assessment method which normally depends on the geological and mining conditions that are revealed prior to mining. There is commonly a certain gap between the assessment results and the real situation. How to combine with the monitoring data in the mining process to get more realistic evaluation results is a problem that needs to be further solved. To this end, this work proposes a static-dynamic coupling rockburst risk assessment method taking into account the geological and mining conditions as well as the monitoring data, and the method has been being applied in typical panels in near-vertical coal seams. Firstly, a static evaluation method used before mining based on the improved comprehensive index method is proposed. The evaluation indicators contained in the comprehensive index method are linearly normalized to obtain the single indicator risk index. The AHP method is used to assign weights to each evaluation indicator, and the weighted summation of all indicator risk indexes is calculated to obtain the risk indexes determined by geological factors and mining technology factors, respectively. Then the weighted mean of the two risk indexes is used as the static evaluation risk index. Secondly, a dynamic evaluation method used during mining by utilizing the monitoring data is constructed. According to the characteristics of microseismic monitoring and borehole stress monitoring and their relationship with rockburst risk, the dynamic evaluation indicators are constructed based on the microseismic energy density and borehole stress variation. The evaluation indicators are linearly normalized to obtain two evaluation indexes. The weighted mean of the two indexes is used as the dynamic evaluation risk index. Finally, the two proposed methods are combined to get a static-dynamic coupling evaluation model. The coupling evaluation risk index is obtained by weighted average of the static evaluation risk index and the dynamic evaluation risk index, and then the risk grade and risk area are determined. The method is applied in +450B3+6 panel of Wudong Coal Mine. Results show that the static evaluation method demarcates 4 medium risk areas and 1 weak risk area before the mining of the panel, the dynamic evaluation method determines that the rock pillar side has high risk level in the mining process of the panel, and the static dynamic coupling evaluation re-evaluates the weak risk area of the static evaluation to the medium risk area. By investigating the monitoring data of support pressure, the numerical simulation results and the rockburst occurrence on site during the mining process of the panel, the evaluation results are verified, and it is found that the static and dynamic coupling evaluation results are more consistent with the actual situation. This work provides a new method and a new idea for the risk assessment of rock burst.

     

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