基于临界应力指数法巷道冲击地压危险性评价

Evaluation on the rock burst risks of roadway using critical stress index method

  • 摘要: 冲击危险性评价的目的是确定待采掘区域的冲击地压危险等级及范围,是冲击地压防治工作的基础。 建立了“应力-围岩-支护”巷道冲击地压力学模型,发现了巷道冲击地压发生的临界应力、临界阻力区深度与煤体单轴抗压强度、巷道支护强度、巷道几何参数以及冲击能指数4者之间的内在关系。冲击能指数直接影响巷道围岩系统结构失稳的临界应力与临界阻力区的大小,阻力区深度增加导致冲击地压发生的临界载荷增加,实际阻力区深度与应力环境是影响冲击地压发生的重要因素。给出了考虑了煤体的实际应力环境、煤体冲击倾向性、巷道结构属性及实际围岩状态4个因素的临界应力指数计算方法。提出采用临界应力指数评价巷道冲击地压危险性的方法,将相似条件下已经发生过冲击地压区域的临界应力指数,作为待评价区域的冲击地压发生指标Kfcr,把临界应力指数在0,Kfcr区间以0.25Kfcr为间隔,划分为4个数值区间,由低到高分别对应无冲击危险、弱冲击危险、中等冲击危险和强冲击危险4个危险等级,依据临界应力指数在4个区间的分布情况判定待评价区域的危险等级。 以某矿303工作面实际工程为案例,介绍了包含10个步骤的冲击危险性评价流程,评价结果表明:该工作面存在中等冲击危险区域5个,强冲击危险区域7个。钻屑法监测数据表明评价结果与现场实际相符。与综合指数法评价结果相比,临界应力指数法的评价结果更趋于量化。

     

    Abstract: Rock burst hazard evaluation refers to the confirmation of the rock burst hazard grades and dangerous areas, which is the foundation of rock burst prevention. The “stress-surrounding rock-support” model for roadway rock burst was established. Based on the rock burst theory of disturbance response instability,the internal relationships among the critical stress,the depth of critical resistance zone,the uniaxial compressive strength of coal mass,the support strength of roadway,the geometric parameters of roadway and the impact energy index were found. The impact energy index directly affects the size of the critical stress and critical resistance zone of the roadway surrounding rock system. The increase of the depth of the resistance zone leads to the increase of the critical load of the rock burst. The actual depth of the resistance zone and the stress environment are the important factors affecting the rock burst. The calculation method of the critical stress index considering the in-situ stress environment,the outburst proneness of the coal mass,the struc- tural property of the roadway and the actual surrounding rock state was given. The critical stress index at the area where the rock burst occurred with similar conditions was taken as the rock burst occurrence index Kfcr of the area to be evaluated,and the critical stress index is divided into four nu-merical intervals with 0. 25 Kfcr as the interval in0, Kfcr ,corresponding to the four risk grades of no hazard,weak hazard,medium hazard and strong hazard,respectively. The rock burst hazard of the area to be evaluated is determined according to the distribution of the critical stress index in the four intervals. Taking the 303 working face of a mine as an example,this paper introduces the process of rock burst hazard evaluation which includes 10 steps. The evaluation result shows that there are 5 areas with medium hazard and 7 areas with strong hazard in this working face. Compared with the comprehensive index method,the evaluation results of critical stress index method tend to be more quantitative,and the monitoring data of the drilling bits method show that the evaluation results are consistent with the results of field monitoring.

     

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