Abstract

Response characteristics of key strata during the periodic weighting process in Dongjiahe coal mine were investigated using micro-seismic (MS) monitoring. Fracture types of key strata were identified through the moment tensor inversion. Finally, fracture mechanism of roof key strata was revealed from a microscopic viewpoint. The results show that there are three concentrations of MS events distributed along the dip direction. And two MS event clusters were formed in “pairs” before and behind the working face. Along the strike direction, tensile and shear factures occur in front of the working face with a dip angle of 54°, while the micro-fractures are mainly mixed and partial shear types behind the working face. By contrast, the rock fracture usually occurs behind the working face along the dip direction. The micro-fractures are mainly tensile and mixed types before fracturing compared to mainly mixed and shear fractures with slight tensile ones after fracturing. The fracture pattern basically conforms to the “O-X” type. The X-shaped fracture extends outward with an angle of 46° with the due north. The findings in this paper provide a theoretical reference for strata behaviours and hazard risk assessment under similar conditions.

摘要

采用微地震（MS）监测方法研究了董家河煤矿周期性加权过程中关键地层的响应特征。通过矩张量反演识别了关键地层的裂缝类型。最后，从微观角度揭示了顶板关键地层的破裂机制。结果表明，沿倾角方向分布有3个浓度的MS事件。并且在工作面前后“成对”形成了两个MS事件簇。沿走向，工作面前倾角为54°的拉剪断裂发生，而工作面后的微裂缝以混合型和部分剪切型为主。相比之下，岩石断裂通常沿倾角方向发生在工作面后方。压裂前微裂缝以拉伸型和混合型为主，压裂后以混合型、剪切型为主，微张型为主。断口形态基本符合“OX”型。X形裂缝向外延伸，与正北成46°角。本文研究结果为类似条件下的地层行为和灾害风险评估提供了理论参考。