采场顶板破断型震源机制及其分析

ANALYSIS OF FOCAL MECHANISM CAUSED BY RUPTURE OF STOPE ROOF

作为一种区域、实时、动态监测手段,微震监测技术用于预测预报冲击矿压等地质灾害乃至防灾减灾完全可行,而不同震源震动机制的研究是微震法预测预报冲击矿压的前提和基础。采场顶板是影响煤矿冲击矿压发生的重要因素,在分析采场坚硬顶板断裂过程的基础上,建立坚硬顶板断裂震动的等效点源模型,并根据该模型用震动波理论分析坚硬顶板断裂的震动位移方程,揭示了坚硬顶板断裂的震源机制,并通过三河尖矿微震监测的坚硬顶板断裂信号验证分析结果的正确性。研究表明,采场顶板由于受源外介质的拉力作用,断裂时震源会产生波前向外传播的压缩波,震源处岩体破坏主要为张性拉伸破坏。研究结果可为顶板型冲击矿压的预测预报和防治提供理论依据。

As a regional, real-time and dynamic monitoring means, the microseismic monitoring technology is quite feasible to forecast several geological hazards, such as rockburst, mine tremor, coal and gas outburst, and so on. And because of the good expandable nature of this technique, it even can prevent and reduce these disasters. The study on the focal mechanism of different hypocenters or seismic sources is the prerequisite and basis for forecasting rockburst by microseismic monitoring technology. Roof structure, especially hard and thick sandstone roof, is one of the main factors leading to the occurrence ofrockburst. Based on the analysis of the fracture of hard roof, the equivalent point source model of the tremor or rockburst caused by hard roof is Constructed. According to the model, the seismic displacement equation of hard roof is analyzed by using seismic wave theory. Based on the above analysis, the focal mechanism caused by the rupture of roof is pointed out. The microseismic signals of the fracture of hard roof acquired by the microseismic monitoring system in Sanhejian Mine validate the theoretical analysis results. The results show that by the tensile strength of medium nearby the seismic source, the wave field will generate compression wave in the seismic source and induce tensile fracture at the moment of rock breakage, which is different from the style of failure in the coal pillar and fault. The results can be used to provide theoretical basis to forecast and prevent rockburst caused by hard roof.