厚松散层下煤层开采全地层移动变形时空演化特征

Spatio-temporal evolution characteristics of whole strata movement and deformation during coal seam mining under thick loose layers

  • 摘要: 煤炭资源井工开采会引发上覆地层的移动变形,对工业广场建(构)筑物运维、采区规划及矿井安全生产造成严重影响。揭示基岩、松散层与地表三者之间的移动变形差异性及其垂向形变传递特征,对于矿区安全开采与沉陷控制具有重要实践意义。以两淮新集矿区为研究对象,采用分布式光纤感测技术构建全地层监测系统,通过开展三维物理相似模型试验与工程原位测试相结合的方法,利用应变表征数据研究了煤层开采过程中全地层垂向移动过程及其变形分布与演化特征。研究表明:基岩、松散层与地表的移动变形呈现非整体、不连续特征,基岩与松散层内部变形表现出典型的分段性。在变形时序特征上,基岩表现为“陡沉—慢沉—稳沉”的快速传递模式,松散层呈现“缓沉—陡沉—慢沉—稳沉”的含隔水层分段变形模式,而地表则表现为“慢沉—缓沉—稳沉”的非均速渐变移动模式。进一步分析发现,基岩段变形传递速率是松散层段的4.8倍,而基岩段变形传递时间仅为松散层段的0.27倍。现场监测结果表明:全地层沉降构成中,基岩段沉降贡献率为78.4%,松散层段沉降贡献率为21.6%。回采阶段上覆地层受沉积层状结构及疏水共同作用,内部拉伸变形主要集中于采空区上方离层发育区及采空区边界附近,而压缩变形则集中于煤壁前方支承压力影响区。研究结果深化了厚松散层下煤层开采覆岩移动变形传递机制的认识,可为开采过程中从被动沉陷控制转向主动减沉、减损提供数据支撑与科学指导。

     

    Abstract: Underground mining of coal resources induces movement and deformation in the overlying strata, significantly impacting the operation and maintenance of industrial square structures, mining area planning, and mine safety production. Revealing the differences in movement and deformation among bedrock, loose layers, and the surface, as well as their vertical deformation transfer characteristics, holds important practical significance for safe mining and subsidence control in mining areas. The Xinji mining area in the Huainan–Huaibei coalfield is selected as the research area. A distributed optical fiber sensing (DOFS) system was employed to construct a full-strata monitoring system. By combining three-dimensional physical similarity model tests with in-situ engineering measurements, strain characterization data were used to investigate the vertical movement process, deformation distribution, and evolutionary characteristics of the entire strata during coal seam mining. The research reveals that the movement and deformation of bedrock, loose layers, and the surface exhibit non-integrated and discontinuous characteristics, with internal deformation in bedrock and loose layers displaying typical segmentation. The temporal deformation patterns vary significantly, the bedrock follows a “rapid-gradual-stable” subsidence pattern with fast deformation transfer; the loose layers display a “gradual-rapid-gradual-stable” response governed by aquifer-aquitard interactions; while the surface subsidence shows a “slow-gradual-stable” subsidence pattern with non-uniform velocity. Further analysis indicates that the deformation transfer rate in the bedrock section is 4.8 times that of the loose layer section, while the deformation transfer time in the bedrock section is only 0.27 times that of the loose layer section. Field monitoring results show that in the total strata subsidence composition, the bedrock section contributes 78.4%, whereas the loose layer section contributes 21.6%. During coal seam extraction, the overlying strata are influenced by both layered sedimentary structures and dewatering effects. Tensile deformation within the strata is mainly concentrated in the bed separation zones above the goaf and near the goaf boundaries, while compressive deformation is concentrated in the abutment pressure-affected zones ahead of the coal wall. The findings enhance the understanding of the deformation transfer mechanism in overburden strata under thick loose layers during coal mining. They provide data support and scientific guidance for transitioning from passive subsidence control to active subsidence and damage mitigation during mining operations.

     

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