采动覆岩运移BOTDA-FBG监测试验

为研究采场覆岩变形破坏特征,采用相似材料物理模型试验的方法模拟煤矿工作面回采过程,用BOTDA分布式光纤和布拉格光纤光栅(FBG)监测采场覆岩运移规律。实验搭建了1.5 m×0.6 m×1.3 m的三维立体模型,几何相似比为1∶150,同时在模型水平方向埋设2根光纤,垂直方向铺设4根光纤,亚关键层埋设2个光纤光栅应变传感器,用以研究模型开挖过程中覆岩运移状态与BOTDA及FBG测试结果的对应关系。试验表明,FBG传感器应变量与岩层运移状态密切相关,可实现对采动覆岩变形破断和离层发育过程的监测。水平光纤测试结果与岩层垮落移动呈明显的对应关系,测试频移峰值间距与岩层垮落顶部离层宽度几乎一致,平均误差不超过3%;垂直光纤频移变化可以反映覆岩垮落及离层发育的动态变化过程。

BOTDA-FBG monitoring test for mining overburden migration

In order to study the deformation and failure characteristics of mining overlying rocks, similar material physical model test was used to simulate the remining process of coal mine face, and BOTDA distributed optical fiber and FBG were used to monitor the migration laws of mining overlying rocks. The three-dimensional model of 1.5 m × 0.6 m × 1.3 m was built experimentally. The geometric similarity ratio was 1:150. At the same time, two optical fibers were laid in the horizontal direction of the model, four optical fibers were laid in the vertical direction, and two fiber grating strain sensors were laid in the sub-critical layer. It is used to study the relationship between the migration state of overburden rock and the test results of BOTDA and FBG during model excavation. The experiment shows that the strain of FBG sensor is closely related to the migration state of rock formations, and can monitor the deformation breaking and delamination process of mining overburden rocks. The horizontal optical fiber test results showed a clear correspondence with the rock collapse movement. The peak distance of the test frequency shift was almost the same as the width of the upper layer of rock collapse. The average error was not more than 3 %. The change of frequency shift of vertical fiber can reflect the dynamic process of overburden collapse and delamination.