深厚表土煤层冲击地压模式研究

Rock burst is one of the most serious dynamic hazards in deep mining of coal mines. Serious rock bursts happened in Juye mining areas with thick alluvium ground. The rock burst has two characteristics of instantaneous and delay. On the basis of understanding of mining features and ground characteristics of coal seam under thick alluvium, with the method of tracing changes of strata movement field and stress field of coal seam by micro-seismic monitoring and stress on-time monitoring technology, combining numerical and physical simulation, theoretical analysis, laboratory testing and in-site investigation, the project analyses overlaying strata structure and movement characteristics, stress evolution rules in coal mining under thick alluvium and instability features of coal seam under thick alluvium. The relationship of overlaying strata movement, stress evolution and rock burst behaving in coal mining under thick alluvium is expected to be revealed. The rock burst models of coal seam under thick alluvium, “overlying strata structure moving → coal stress evolving → instantaneous burst” and “ground deforming→ coal stress growing → delay burst”, are used to reveal rock burst mechanism in the condition of thick alluvium. According to this project, it is expected to further reveal dynamic source and model of rock burst of coal seam under thick alluvium. The results will provide a theoretical basis for prediction and prevention of rock burst of coal seam under thick alluvium.

冲击地压是我国煤矿深部开采面临的最为严重的动力灾害之一。具有深厚表土地层的巨野煤田发生过严重的冲击地压，并表现出瞬时冲击和延时冲击两类特点。项目结合深厚表土煤层开采特点和地层特征，通过采用微震监测技术追踪岩层运动场动态和采用应力动态监测技术追踪煤层应力场动态，并结合数值与物理模拟、理论分析、实验室试验、现场调研等，首先分析深厚表土煤层开采覆岩结构与运动特征，其次探讨深厚表土煤层开采煤层应力演化规律，然后研究深厚表土煤层破坏失稳特性，从而揭示深厚表土煤层开采覆岩运动、煤层应力演化、冲击地压显现三者之间的联系，表征深厚表土煤层的两种冲击地压模式：“覆岩结构运动→煤层应力演化→瞬时冲击”和“地层变形→煤层应力增长→延时冲击”，用以揭示该类地层条件下煤层冲击机理。期望通过研究，深入揭示深厚表土煤层冲击动力源和模式，为深厚表土煤层冲击地压预测、治理提供理论依据。

深厚表土煤层开采过程中面临严重的冲击地压灾害，且现场表现为瞬时冲击和延时冲击两种模式。本项目采用微震监测、应力监测和相似材料模拟等手段，研究了深厚表土煤层开采覆岩运动、煤层应力演化、冲击地压显现之间的相互关系。结果表明：覆岩运动高度整体上随推采距离的增大向上发展，但存在平台效应；松散表土层也能形成拱形结构，且随着开采范围增大，松散表土层运动范围向上发展；松散表土层运动范围到达地表后，随着开采范围的再次扩大，松散表土层发生周期性的整体失稳，易诱发煤层瞬时冲击；顶板运动范围发展至松散表土层后，在某一推采阶段，表土层运动表现出延时特征，且导致煤层应力演化，易诱发延时冲击；深厚表土采场支承压力分布特征具有峰值大、峰值位置远、低应力区宽度大和影响范围小等特点；深厚表土煤层发生瞬时冲击的过程是“覆岩空间结构运动→煤层应力演化→煤体脆性破坏→冲击”，而发生延时冲击的原因在于覆岩空间结构运动、煤层应力演化、煤体破坏等三者中任意一个阶段程发生延时。在获得上述认识的基础上，提出了5种延时冲击地压模型。. 课题组将获得的上述成果应用于深厚表土煤层冲击地压预测与防治。另外，通过监测、计算与实验等获得支承压力分布特征和煤层破坏特征，可将其用于确定两翼采区大巷煤柱宽度、采场推采速度、冲击地压监测与卸压范围、停采线位置、超前支护距离等。本项目对深部煤层开采冲击地压防治具有重要的现实意义。