特厚煤层沿底巷道顶板离层－失稳灾变模型与控制机理

Bedding separation and its induced roof instability overlying coal roadways driven along coal floor within extra-thick coal seams has become one of the most concerned disasters happened frequently and seriously in various roof control cases during underground coal mining, which has imposed heavy restrictions on extra-thick coal seam mining safely, sustainedly and effectively. The cable truss system has certain advantanges over preventing this type of roadways from roof instability, however, its controlling mechanism is not clear. Therefore, it is evident that research should be developed on the catastrophe mechanism of bedding separation and its induced roof instability overlying coal roadways driven along coal floor, and on roof controlling mechanism of the cable truss system.Theoretical analysis, mechanical calculation, field investigation, analog simulation, numerical simulation and other powful methods will be planned and applied to conduct our research on the bedding separation distribution overlying coal roadways driven along coal floor, dynamic evolution along with the roadway excavation and mining activities, the correlation between bedding separation and induced roof instability when embeded rock layers exsit at different locations, and roof control mechanism of the cable truss for preventing the roof instability and so on. Lots of effort will be devoted towards revealing dynamic evolution of bedding separation overlying coal roadway driven along extra-thick coal seam floor, developing a model characrized on roof bedding separation and its instability, and instability criterion, and illustrating roof control mechanism of the cable truss for preventing the roof instability. The research results have important theoretical and realistic significance on many aspects, such as further developing roof catastrophe mechanism, preventing the serious roof caving accidents and promoting the support technology reform.

特厚煤层沿底巷道顶板离层—失稳灾变是我国煤矿井下各类巷道顶板灾害中发生频率最高和造成伤亡事故最严重的灾害之一，并严重制约着特厚煤层赋存矿区煤炭的安全持续高效开采，而锚索桁架系统在控制特厚煤层沿底巷道顶板失稳方面具有一定优势，但控制机理不清。因此，开展特厚煤层沿底巷道顶板离层—失稳灾变机理和锚索桁架系统控制顶板失稳机制研究非常必要。本项目拟综合运用理论分析、力学计算、现场测试、相似模拟、数值模拟等方法，针对特厚煤层沿底巷道顶板离层分布状态、采掘进程顶板离层演化规律、顶板内不同位置夹矸层时离层与失稳关联性、锚索桁架系统控制顶板力学机理等进行研究，揭示特厚煤层沿底巷道顶板离层动态演化规律，建立可表征随采掘进程顶板离层—失稳灾变模型以及失稳判据准则，阐明锚索桁架系统对顶板失稳的防控机制。研究成果在深化特厚煤层沿底巷道顶板致灾机理、控制恶性冒顶事故及推动支护技术改革方面具有重要的理论意义和实用价值。

本项目针对特厚煤层沿底巷道顶板离层－失稳控制难题，综合采用现场调研、理论分析、相似材料模拟、数值模拟等方法，对特厚煤层沿底巷道顶板离层-失稳演化特征及锚索桁架系统作用机制进行研究。. 项目通过对典型矿区特厚煤层沿底巷道顶板变形特征的大量调研和实测，得出厚煤顶巷道围岩难以控制的主要原因；基于回采过程中特厚煤层沿底巷道顶板存在的节理等非连续结构影响、高水平应力及采动应力影响联合作用，构建了特厚煤层沿底巷道顶板离层位置预测力学计算模型，推导了特厚煤层沿底巷道顶板离层发生位置的公式；分别构建了特厚煤层巷道顶板层间离层和离层-失稳力学计算模型，得出了顶板层间离层上限位置确定所需要满足的荷载条件、极限跨度、挠度条件及顶板关键层位置与离层位置范围的计算式以及顶板离层致失稳过程锚索支护结构破坏判据；在此基础上，根据厚煤顶中夹层与顶板锚杆（索）位置关系，建立相似材料物理模型，模拟得出了不同采动应力条件下特厚煤层巷道围岩演化特征。选择典型特厚煤层回采巷道，现场监测并分析得出了顶板离层孕育发展的主要区域以及横、纵离层的演化特征；采用3DEC模拟软件分析了随采动过程特厚煤层回采巷道围岩顶板离层和应力的分布规律；结合特厚煤层巷道支护系统—顶板岩层协调作用关系，分别建立了厚煤顶锚索桁架支护和无支护下顶板变形计算力学模型，推导了采用锚索桁架系统及无支护时顶板最大下沉和离层量、采用锚索桁架前后顶板最大下沉和离层减小量计算式；采用ABAQUS软件模拟比较了锚索桁架系统与锚杆/索支护方式下特厚煤层沿底巷道顶板的应力场、位移场和塑性区范围分布特征，阐明了锚索桁架支护特厚煤层巷道顶板的优越性，为锚索桁架系统在特厚煤层沿底巷道运用提供理论支撑；最后将锚索桁架系统在典型特厚煤层沿底巷道进行了成功实践。. 通过理论分析、数值模拟、力学计算、现场试验结果分析等，最终得到了特厚煤层回采巷道顶板离层演化特征及锚索桁架系统对厚煤顶的作用机理。