光纤频移变化度表征采动覆岩变形基础研究

Controlling the stope roof is the key to achieving safe production and management of coal mines. Due to the complex deformation and failure process of mining overburden, the monitoring of the overburden deformation and movement processes under mining conditions is conducive to the control of strata under complex engineering environments. In this project, the optical fiber sensing detection of mining overburden deformation is taken as the research object. From the perspective of mathematics, mechanics, and optics, the expression of distributed optical fiber frequency shift variation is used to characterize the large deformation of mining overburden deformation. The strain-transmitting mechanism of fiber-cover-rock in optical fiber sensing process of mining overburden under elasto-plastic, plastic and fissure deformation states is studied. The influencing factors and spatial reliability of the optical fiber frequency shift variation degree to characterize mining overburden deformation are studied. Study the characteristic data to identify the degree of change of the optical frequency shift. By carrying the rock specimens uniaxial compressive and shear numerical simulation experiments and the physically similar material model orthogonal experiments, characterization of mining overburden evolutionary structure by optical fiber frequency shift variation degree is studied under the influence factors of mining height, coal bed burial depth, and key stratum position. Synergetic deformation relationship between mining overlying strata and optical fiber is established. The research results are significant for providing information to define the “three-zone” structure, monitor surrounding rock stability, and to study the mining subsidence.

采场顶板控制是煤矿安全生产管理的重点，上覆岩层变形与破坏过程复杂，实现采动条件下覆岩变形状态和运动过程的测试有助于复杂工程环境下的岩层控制。本项目以采动覆岩变形的光纤传感检测为对象，从数学、力学和光学的角度建立适用于采动覆岩大变形表征的分布式光纤频移变化度表达方式，研究覆岩弹塑性、塑性、裂隙变形状态下光纤感测过程中光纤-封装材料-岩石的应变传递机理，研究光纤频移变化度用于覆岩不同变形表征的影响因素、空间可靠度；研究光纤频移变化度特征数据辨识。开展岩石试件单轴抗压、抗剪数值模拟实验，物理相似材料模型正交实验，研究采高、煤层埋深、关键层位置多因素影响下，光纤频移变化度对采动覆岩演化结构的表征；建立采动覆岩与光纤协同变形关系。研究成果对“三带”结构的空间界定、围岩稳定性监测、开采沉陷的研究，具有重要科学意义。

采场上覆岩层的变形过程是矿山压力驱动下的复杂变形与破坏，导致对采场覆岩的变形状态难以测试、岩层变形和运动过程难以表征。工程实践对覆岩变形测试与状态描述提出了更高的要求，需要发展能适应采场上覆岩层大范围变形特性的测试技术和表征方法。实现采动条件下覆岩变形状态和运动过程的测试有助于复杂工程环境下的岩层控制。. 本项目以覆岩变形破坏光纤表征研究为目标，提出了光纤频移变化度的概念，通过对某空间区段内光纤临界两个频移数据采集样本的差值进行均一化处理，得到监测区段光纤频移样本差异程度，用以表示某空间区段内岩体结构变形和运动的剧烈程度。建立了采场关键层破断光纤表征力学模型，实现了处于固支梁形态的关键层、关键层初次破断、周期破断和完全破坏时不同变形特征光纤表征。建立了光纤频移变化度与工作面来压表征模型，随工作面开挖光纤频移变化度曲线出现峰值时，工作面发生来压。通过相似材料物理模型试验工作面支承压力监测与光纤频移变化度来压表征结果对比，验证了光纤频移变化度表征工作面来压的正确性。提出工作面来压空间可靠度概念，不同覆岩空间位置处与覆岩全段空间的光纤频移变化度来压表征次数的比值，以表示对工作面来压表征的可靠程度。开展了巨厚砾岩覆岩变形三维相似材料模型试验，研究表明采用巨厚砾岩段、砾岩以下覆岩光纤频移变化度对工作面来压进行表征，为工作面来压光纤表征试验研究和工程应用提供依据。开展了近距离煤层群上保护层开采底板卸压光纤表征工程应用研究，基于光纤传感监测实现了葫芦素煤矿保护层开采的卸压范围及效果评价，基于光纤应变增量指标将卸压过程划分为三个阶段。. 随着煤炭开采规模化和集约化建设，催生了采场大空间、覆岩大变形、岩移大范围的覆岩变形新特点，造成工作面矿压显现剧烈、围岩支护难度增大等岩层控制新问题。本项目研究成果对于覆岩变形精准信息掌控、围岩稳定性控制、覆岩“三带”划分、开采沉陷研究等具有重要意义。