Distribution Measurement and Mechanism Research on Deformation due to Losing Water of Overburden Layer

Based on FBG fiber Bragg grating technology and BOTDA distributed optical fiber sensing technology, this study used fine sand to simulate overburden layer in vertical shaft model equipment. The placing technique and test method for optical fiber sensors in the overburden layer were studied, combined with MODFLOW software to simulate the change of the water head value when the overburden layer was losing water, and obtained the deformation features of overburden layer. The results showed that at the beginning of water loss, the vertical deformation increased due to larger hydraulic pressure drop, while the deformation decreased gradually and tended to be stable with the hydraulic pressure drop reducing. The circumferential deformation was closely related to the distance between the drainage holes, variations of water head value and the method of drainage. The monitoring result based on optical fiber sensing technology was consistent to the characteristics of water loss in overburden layer simulated by MODFLOW software, which showed that the optical fiber sensing technology applied to monitor shaft overburden layer was feasible.