In Situ Monitoring and Analysis of the Development Characteristics of Separation in Internal Overburden

This study conducted in situ monitoring by means of distributed optical fiber sensors (DOFS) and multipoint borehole extensometers (MPBXs). Combined with the measurement data of water level depth, the development of separation was analyzed comprehensively for the first time. At first, the development height of the water-conducting fracture zone was predicted. As the results show, the predictive data is 173.95 m. According to the in situ monitoring data, the top boundary height of the water-conducting fracture zone is determined at a height of 186.1~207.9 m, which is in line with the predicted results. Based on the DOFS data, it can be inferred that the separation layer exists at the depths of 351.3~390.4 m. According to MPBXs data, the largest development of the separation layer is also inferred to be located at the depths of 324~388 m. The in situ monitoring methods in this study can directly obtain the development position of the separation layer in the internal overburden, which can provide good guidance for the on-site control of water disasters caused by water accumulation in separation.