基于分布式光纤技术的采动影响下覆岩变形演化规律试验研究

为了解决在实际工程中岩层变形难以用常规测试方法进行监测的问题,采用分布式光纤传感技术的布里渊频域分析技术(BOFDA)和布里渊频移(BFS)分析技术,根据现场的煤层采动过程,在试验室建立4200 mm×250 mm×1600 mm(长×宽×高)的采场覆岩模型,通过预埋于模型内部的4条水平传感光纤和5条垂直传感光纤,对模型开挖过程中的覆岩变形特征进行测试。将光纤测试结果与近景摄影数字图像处理技术获得的岩层位移进行对比,揭示了光纤频移值和岩层工作面来压及覆岩结构演化的对应关系,获得了基于光纤频移值的两带发育、演化范围的表征方法。研究表明,使用BOFDA分布式光纤技术监测采动覆岩活动特征与矿压显现规律是可行的,试验结果为分布式光纤测试技术在现场监测煤矿上覆岩层"两带"变形提供了理论依据与试验保障。

Experimental study on overburden deformation evolution under mining effect based on distributed fiber optical sensing technology

In practical engineering,the overburden deformation is difficult to be monitored by conventional testing methods.Therefore,the Brillouin frequency shift(BFS)analysis and Brillouin optical frequency domain analysis(BOFDA)technology are adopted in this research to solve the problem.Based on the coal mining processes in the field,a 4200 mm×250 mm×1600 mm(length,width and height,respectively)overlying strata model is established in the laboratory.The deformation charactistics of overlying strata during the excavation are tested through the four horizontal sensing fibers and five vertical sensing fibers embedded in the model.By comparing the experimental results with the measured displacements obtained by close range photography digital image processing technology,the relationships between the optical fiber frequency shift values,strata working face weighting and the evolution of overburden structure are revealed through the comprehensive analysis of the characteristics of mining overburden activity and the law of strata pressure appearance.Besides,the characterizing method of the development and evolution range of two zones based on optical fiber frequency shift value are also obtained.The study shows that the BOFDA technology can be used to monitor the characteristics of mining overburden activity and the law of strata pressure appearance using BFS analysis.The test results provide theoretical and experimental support for the field application of distributed optical fiber testing technology in monitoring the"two zones"deformation of overlying strata in coal mines.