浅埋大采高采场覆岩−地表联动损伤传导规律研究

Research on coordinated damage conduction of overburden-surface in large mining height working faceof shallow coal seam

  • 摘要: 研究大采高开采条件下岩层结构运动与地表移动变形的链式传导关系,对西部高强度开采矿区煤炭资源合理开发、区域环境保护及生态修复等具有重要意义。基于关键层理论构建了3类典型大采高采场物理相似实验模型,获得了大采高采场关键层结构特征、失稳运动型式及交替演化规律。通过理论分析揭示了关键层结构与损伤传导的耦合机制,明晰了损伤传导路径的空间展布规律与动态演化特征。最后结合现场调研建立了覆岩运动模式与地表损害表征的关联关系。结果表明:大采高采场关键层结构主要分为“悬臂梁”结构、“砌体梁−悬臂梁”结构以及“双砌体梁”结构,其中Ⅰ、Ⅱ型采场处于覆岩垮落带中的关键层破断后一般形成“悬臂梁”结构,此结构的运动发展过程并非一成不变,而是多数时间存在交替演化现象,表现为“悬臂梁”、“台阶岩梁”、“砌体梁”多种结构形态的交替破断运动。关键层“悬臂梁”结构时损伤传导表现出瞬时突变与单一路径特性,关键层“砌体梁−悬臂梁”结构时损伤传导表现出下层触发、上层调控及多路径阶梯跃迁特性,关键层“双砌体梁”结构时损伤传导表现出多重调控与内部耗散特性,关键层“悬臂梁”结构交替演化时损伤传导路径由单通道突变转为层状递进。Ⅰ型采场受单一主关键层滑落失稳影响,覆岩−地表呈现“整体切落式”破坏,地表以塌陷型裂缝为主;Ⅱ型采场主关键层“砌体梁”结构发生回转失稳,覆岩−地表呈现“裂隙贯通式”破坏,地表主要发育水平张裂的拉伸型裂缝;Ⅲ型采场主关键层发生小角度破断铰接,覆岩−地表呈现“弯曲下沉式”破坏,地表以连续变形为主,局部发育下行拉伸裂隙;亚关键层“悬臂梁”结构交替演化时,块体叠置错动传导至主关键层及地表,是造成Ⅱ型采场异常发育有塌陷型裂缝的主要原因。

     

    Abstract: Studying the chain conduction relationship between strata movement and surface damage in large mining height working faces is of great significance for the “rational development of coal resources, regional environmental protection, and ecological restoration” in western high-intensity mining areas. Based on the key stratum theory, three types of typical physical similarity experimental models for large mining height working face were constructed, and the structural characteristics, moving types, and alternating evolution laws of the key strata were obtained through experiments. Through theoretical analysis, the coupling mechanism between key stratum structure and damage conduction was revealed, and the spatial distribution patterns and dynamic evolution characteristics of damage conduction paths were clarified. Finally, combined with field investigations, the correlation between overburden movement patterns and surface damage characterization was established. The results show that the key strata structure of large mining height working face is mainly divided into “cantilever beam” structure, “voussoir beam−cantilever beam” structure and “double voussoir beam” structure. Type Ⅰ and Ⅱ working faces generally form a “cantilever beam” structure after the key strata in the overburden collapse zone break. The movement and development process of this structure is not invariable, but there is an alternative evolution phenomenon most of the time, which shows the alternative breaking movement of various structural forms such as “cantilever beam”, “step voussoir beam” and “voussoir beam”. The damage conduction in the working face where the key stratum forms a “cantilever beam” structure exhibits instantaneous mutation and single-path characteristics. The damage conduction in the working face where the key stratum forms a “voussoir beam−cantilever beam” structure exhibits characteristics of lower layer triggering, upper layer regulation, and multi-path step transition. The damage conduction in the working face where the key stratum forms a “double voussoir beam” structure exhibits multiple regulation and internal dissipation characteristics. During the alternating evolution of the “cantilever beam” structure of the key stratum, the damage conduction path transitions from single-channel mutation to layered progression. In Type Ⅰ working faces, the sliding instability of the single primary key stratum induces a full-thickness shear failure of the overburden strata and surface, accompanied by the formation of collapse-induced surface fractures. In Type Ⅱ working faces, the rotational instability of the primary key stratum induces a full-thickness fissure penetration failure of the overburden strata and surface, accompanied by the formation of tensile-induced surface fractures. In Type Ⅲ mining faces, the low-angle fracture hinge of the primary key stratum induces bending-subsidence failure in the overlying strata and surface, characterized by predominantly continuous deformation with localized tensile-induced surface fractures. The alternating evolution of the cantilever beam structure in sub key strata induces block superposition and dislocation, which transfers through the primary key stratum to the surface, resulting in dislocation-propagated surface fractures abnormally developed in Type II working faces.

     

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