Calculation model of overburden rock failure volume in mined-out area based on Brillouin optical time-domain analysis technology.

• An overburden failure volume calculation model based on the BOTDA was established. • The optical fiber mechanical models in different zone of overburden are established. • This research is a combination of mining engineering and fiber optic sensing. The determination of overburden failure volume is a great challenge because of the complexity and concealment of mining fractures. Taking the 61,601 working face of Longwanggou Coal Mine as the engineering background, this paper established a two-dimensional model of 3000 mm × 200 mm × 1350 mm (length × width × height) in the laboratory. By adopting the Brillouin optical time-domain analysis (BOTDA) technology, considering the fiber deformation and the coordination of rock strata, Of deformation and damage state of overburden strata above the mined-out area, discusses the strata deformation partitioning features and characteristics of fiber optic monitoring strain curve partition interaction relations, is derived based on the above theoretical calculation formula of the rock damage volume, comparing the calculated results with measured results, verify the accuracy of volume calculation formula of mined-out area. The results show a good correspondence between the strain zoning characteristics monitored by optical fiber and the deformation zoning characteristics of overburden. Based on considering the discordant deformation between the overlying rock mass and the optical fiber sensor, the range and degree of overlying mining rock can be obtained through the inversion of the horizontal optical fiber monitoring results to reflect the position and degree of rock strata movement and deformation with the optical fiber. By analyzing the development process of the vertical fiber optic strain curve, it can be found that the rock strata with different propelling distances and different heights bear different tensile stresses, which have remarkable range characteristics. By comparing the results of the calculation model proposed in this paper with the monitored values of the model, it is found that the void volume size of goaf is the same, and the relative error is less than 9%. The results show that the model is reliable in calculating the failure volume of overburden rock in goaf. [ABSTRACT FROM AUTHOR]