Study On Fiber Bragg Grating Monitoring Of Unconsolidated Strata Subsidence Deformation Of Baodian Coal Mine

The deformation and failure of main and auxiliary shafts in Baodian Coal Minefrequently occurred, it seriously affected the normal production of the mine. On the basis ofthe condition of formation near the main shaft and auxiliary shaft and the position of the shaftdeformation and destruction, we obtained that the subsidence deformation of unconsolidatedstrata caused by long-term continuous decline of aquifer water level of the unconsolidatedstrata in the Quaternary system was the main reason that cause the shaft deformation andfailure.In theory the dewatering compression features of sand, gravel and clay layer are analyzedwith different depth. It was concluded that dewatering compression in the aquifers such as thedeep sand and gravel layer was the main cause of the deformation and subsidence ofunconsolidated strata. The relationship between the water level and the subsidencedeformation of unconsolidated strata is established. The relationship formula between thewater level drop and the strain variation is derired. Further analysis is perform on the physicaland mechanical properties of the clay with high depth. The deep clay layer may be weakenedby aquifer and produce large compression deformation. By the theoretical of unconsolidatedstrata dewatering subsidence calculation model, the relationship between the stratadeformation and surface subsidence is established. The design and installation of stratasubsidence deformation Fiber Bragg Grating monitoring system in the unconsolidatedintroduced to the Baodian Coal Mine. Based on analysis of the strain transitive relationship ofoptical fiber sensing, the transitive relationship between the strain of unconsolidated strata andFBG sensor is obtained.Based on theoretical research, the monitoring results during the installation process of thesystem is analyzed, obtained that each sensor’s wavelength drift amount have a large change,after the completion of the installation process, all returned to the level of close to the initialvalue. Each layer’s strain change, the relationship between unconsolidated strata’s strain and the change of the depth, the characteristics of the strain change of the aquifer such as the sandand gravel layer and clay layer and the weakening characteristics of the aquifer to the claylayer were analyzed. the velue of unconsolidated strata subsidence deformation is calculatedand the parts of the shaft where deformation and damage may occur is predicted. Thecomparative analysis between the strain of the unconsolidated strata and the change of waterlevel is established. Studies show that the Fiber Bragg Grating Monitoring system ofunconsolidated strata subsidence deformation can effectively detect the deformation law ofunconsolidated strata, and at the same time, the system can monitor the weakening of theaquifer to the clay layer.