Meitan kexue jishu (Jul 2023)
Multi-parameter fine sensing method of deformation and failure process of coal seam mining floor
Abstract
Sensing the floor deformation and damage process by testing parameters during coal seam mining is an effective way to secure the geology of the quarry. A numerical model of coal seam mining floor failure was constructed by using the finite difference method to obtain the distribution and evolution characteristics of the plastic zone, which showed a floor failure depth of 21 m. Electric Cables and distributed optical fibers were implanted in the coal floor borehole, and the characteristic parameter profiles under the mining effect were obtained through the continuous acquisition of electrode current values and optical fiber strain values to further analyze the deformation and failure. The result showed that the initial value of electrode current was above 40 mA, and the current value increases slightly as the working face advances, and when the working face advances near the borehole, the current value dropped to less than 1 mA and the rock formation was failure; as for the fiber optic test, the fiber optic strain value increased continuously as the working face advances, and the peak fiber optic strain was 8.589×10−3 when the working face was near the monitoring borehole, after which the rock formation ruptured and the energy was released, and the fiber optic The strain value bounced back after the rock rupture and energy release. The mapping of electrode current and fiber optic strain parameters showed that the deformation and failure process of the floor was divided into four stages, namely, no impact stage, micro impact stage, significant impact stage, and failure stage. The monitoring data provided a good characterization of the deformation and failure process of the floor, but there were some differences, specifically in the perception of the overstress and the beginning of rupture, with the response of the electrode current slightly earlier than the fiber optic strain. The results of the electrode current showed that the floor failure depth was 20.8 m, and the results of the fiber optic strain showed that the floor failure depth was 21 m. The kernel density maps of electrode current values and strain values were constructed. For the monitoring points in the shallow part of the floor, the data points were more discrete; while the monitoring points in the deeper burial were less affected by the dynamic effect, and the data points were more concentrated and less discrete during the recovery process. Through the joint sensing of multiple test parameters, we can realize the fine characterization and evaluation of the deformation and failure process of the coal seam mining floor.
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