基于光纤感测的采动覆岩裂隙演化与表征研究

Overburden mining fracture is the main channel of fluid in rock mass. The distribution and evolution of overburden water-conduction and gas-conduction fissures have concealed and multi-scale characteristics, and it is difficult to be directly tested and evaluated. Study on the evolution and characterization of mining fracture is the key to solve the problems of high-efficiency gas extraction and water resources protection. In this project, the evolution of mining overburden fracture based on optical fiber sensing detection is taken as the research object. According to the requirement of monitoring the water seepage in stratum fracture after the development of water-conducting fracture, the preparation and sensing characteristics of a new type of optical fiber humidity sensor are studied. The strain transmit rule of sensing fiber-binder-rock during the evolution of overburden fractured zone is studied, and the identification and characterization of the evolution of overburden fracture zone based on optical fiber sensing method. Optical fiber humidity sensitive characteristic test, annular shear test, uniaxial compression test, interface pull-out test and numerical simulation test are carried out. Orthogonal experiment of physical similar material model is carried out to realize the identification of optical fiber sensing characterization of the formation, development and evolution processes of overburden mining cracks, and the optical fiber characterization and identification system of overburden mining fractured zone is established. The research results are of great scientific significance to gas scientific extraction utilization and the protection and utilization of water resources.

覆岩采动裂隙是岩体内部流体的主要通道，覆岩导水、导气裂隙分布及演化具有隐蔽、多尺度特征难以直接测试评价，研究采动裂隙演化表征是解决瓦斯高效抽采和水资源保护等问题的关键。本项目以采动覆岩变形裂隙演化的光纤传感检测为研究对象，根据导水裂隙发育后水在裂隙、岩层中的渗流的监测需要，研究新型光纤湿敏传感器的制备及传感特性，研究覆岩变形裂隙带演化过程的光纤感测的光纤-粘结剂-岩石的应变传递规律，研究光纤感测方法用于覆岩变形裂隙带演化特征的辨识和表征。开展光纤湿敏传感特性试验、环形剪切试验、单轴压缩试验、界面拉拔试验以及数值模拟实验，物理相似材料模型正交实验，实现覆岩采动的裂隙形成、发育及演化过程的光纤感测表征辨识，建立采动覆岩裂隙带的光纤表征和辨识体系。研究成果对瓦斯科学抽采和水资源保护利用具有重要科学意义。

本项目以采动覆岩变形演化过程的光纤监测方法为研究对象，得到光纤传感器的应力应变传感和疲劳特性，研制了用于干-湿状态监测的光纤湿敏传感器，提出了覆岩变形光纤传感方法，揭示了不同干湿状态、界面裂隙差异的光纤-岩石应变传递关系。.采用吸湿-放湿实验对研制的光纤湿敏传感器的传感特性进行了研究，采用研制的光纤湿敏传感单元测量了干湿状态，借助三点弯曲实验和拉-拉疲劳实验分析了光纤的应力疲劳特性。采用数值计算方法、试件力学性能实验、界面耦合实验研究了光纤-粘结剂-岩石的应力应变传递特性。通过物理相似模拟实验、数值计算方法和工业实验，研究不同因素影响下的采动覆岩变形的发育演化过程。研究光纤传感单元的应力应变传感特性，并从光纤纤体疲劳、封装层疲劳两个角度来研究光纤传感单元在重复加载下的应力疲劳特性。研究了在不同干湿状态下，针对不同倾角、数量和分布方式的预制裂隙的光纤-类岩石块体的接触界面，分析了光纤传感单元-粘结剂-岩石的应变传递机理，得到干湿状态、界面裂隙特点、岩石特性、粘结剂特性对应变传递特性的影响规律。研究了采高、推进速度、倾角等因素对采动覆岩的离层率、贯通度、下沉量、裂隙密度、垮落范围的形态特征参数的影响规律，以此对采动覆岩区域进行划分，构建多因素影响下采动覆岩变形的演化模型。开展了煤层开采过程中上覆岩层移动规律研究，得到了开采扰动对覆岩变形的影响规律，是西部矿区特别是陕蒙交界榆神府煤田的保水开采的实施基础，对解决西部生态脆弱地区大规模煤炭生产与生态环境保护之间的矛盾和国家能源战略西部转移及可持续发展有着重要意义。