薄基岩工作面覆岩破坏电性响应特征及动态监测技术

Electrical response and dynamic monitoring of overburden failure in thin bedrock working face

  • 摘要: 厚松散层薄基岩开采易导致工作面与松散含水层沟通,造成严重威胁煤矿生产安全的突水溃砂事故,亟需准确获取覆岩破坏发育情况。因此,以河南焦作矿区16041典型薄基岩工作面为研究对象,利用采动力学数值模拟、电法相似物理模拟与现场监测,开展薄基岩工作面覆岩破坏电性响应特征及动态监测技术研究。采动力学数值模拟和电法相似物理模拟结果清晰呈现了垮落带、导水裂隙带发育规律及典型响应特征。现场监测首先采用井下三维并行电法技术获取工作面基岩厚度三维空间分布形态,指导监测孔选址于停采线附近;进而利用并行电法远程监测系统,实现激励电场与自然电场的主被动地电参数同步采集。面对监测钻孔在基岩界面附近成孔性差导致监测高度不足的问题,提出融合超前探的视电阻率变化率动态成像技术,将有效监测高度延拓至75 m,突破钻孔物理盲区限制,并通过全空间反演交叉验证可靠性。现场监测结果表明,垮落带于随采监测中期压实稳定,实测高度18.5 m,止于二1煤层顶板上方砂质泥岩层内;导水裂隙带随开采推进持续向上扩展,后期达最大高度46 m,贯穿整个薄基岩层并延伸至第四系松散黏土层底部,可能形成直接沟通含水层的突水风险通道。厚松散层薄基岩覆岩采动破坏电性演化特征表现为,覆岩破坏的超前损伤可造成电场分布改变,回采位置刚触及电法监测区域时(电法监测区未有明显的覆岩破坏),视电阻率呈现整体升高;强扰动区对应于垮落带,视电阻率变化最大,其呈现出中期稳定的特征;弱扰动区对应于导水裂隙带,视电阻率变化弱于垮落带,其发育范围清晰,发育过程呈现后期稳定的情况,符合采动覆岩破坏中期垮落压实稳定、后期导裂向上扩展的阶段性规律。本研究构建的“采前静态探测(三维电法查明基岩厚度)−采中动态监测(钻孔超前探测延拓盲区)”技术模式,可解决薄基岩工作面覆岩破坏监测现场难题,实践证实该模式能够有效揭示垮落带与导水裂隙带的发育高度、空间形态特征,并有助于评估潜在的突水风险,为华东地区类似水文地质条件煤矿防治水及安全回采提供了关键技术支撑。

     

    Abstract: Coal seam mining under thick unconsolidated layers and thin bedrock can lead to hydraulic connections between the working face and the overlying unconsolidated aquifer, potentially inducing water inrush and sand outburst disasters that severely threaten mine safety. Therefore, accurately characterizing the development of overburden failure is crucial. Using the 16041 working face in the Jiaozuo mining area of Henan Province as a case study, we combined numerical mining dynamics simulation, physical modeling with electrical similarity, and field monitoring to investigate the electrical response characteristics and dynamic monitoring techniques for overburden failure in thin-bedrock working faces. Both the numerical and physical modeling results clearly revealed the development patterns and typical electrical response characteristics of the caved zone and water-conducting fracture zone. During field monitoring, we utilized underground three-dimensional parallel electrical methods to determine the spatial distribution of bedrock thickness, which guided the layout of monitoring boreholes. We then applied a remote parallel electrical monitoring system to synchronously acquire both active and passive geo-electrical parameters. To overcome poor borehole formation and insufficient monitoring height near the bedrock interface, we developed a resistivity variation based dynamic imaging technique integrated with advanced detection. This method extended the effective monitoring height to 75 m, overcame the physical blind zone of the boreholes, and enabled cross-validation through full-space inversion. Field monitoring showed that the caving zone became compacted and stabilized during the mid-mining stage, with a measured height of approximately 18.5 m, terminating within the sandy mudstone above the No. 21 coal seam roof. The water-conducting fracture zone continued to propagate upward during the late mining stage, reaching a maximum height of 46 m, penetrating the entire thin bedrock layer and extending to the base of the Quaternary clay layer, potentially forming a direct water inrush pathway. The electrical response analysis indicates a distinct staged evolution during overburden failure: pre-mining damage caused an overall increase in apparent resistivity; the strong disturbance zone, corresponding to the caving zone, showed the largest resistivity variation and mid-term stability; the weak disturbance zone, corresponding to the water-conducting fracture zone, exhibited smaller resistivity variations but a clearly defined range and late-stage stabilization. These results are consistent with the staged overburden evolution characterized by mid-term compaction of the caving zone and late-stage upward expansion of the fracture zone. We developed an integrated monitoring approach combining pre-mining static detection, using three-dimensional electrical methods to determine bedrock thickness, with mid-mining dynamic monitoring, employing advanced borehole probing to extend beyond blind zones. This approach addresses the challenges of overburden failure monitoring in thin-bedrock working faces. Field application demonstrated that the method can accurately reveal the developmental height and spatial morphology of the caving zone and the water-conducting fracture zone, and support the assessment of potential water inrush risks, providing key technical guidance for water hazard prevention and safe mining in coal mines under similar hydrogeological conditions in East China.

     

/

返回文章
返回