Comparative study on the “optic-electric” monitoring method for the deformation and failure of surrounding rock in stopes

The evolution law for the mining-induced deformation and failure of surrounding rock is an important parameter for coal mine work safety. Accurate detection is a scientific matter worthy of in-depth study. A 4 m × 1.5 m × 0.4 m planar stress similarity model was built to simulate the excavation of a coal seam, with a total advance distance of 2.05 m. A Brillouin optical time domain analysis (BOTDA) sensing optical cable and 128 resistivity sensor units embedded in the model were used to dynamically monitor the internal deformation of the model and comparatively analyze the evolution characteristics of the strain field and geoelectric field under mining conditions, thereby revealing the development mechanism of the deformation and failure of the rock stratum. The test results showed that with the fracture of the rock stratum and the opening and closing of the abscission layer, synchronous deformation inside the rock stratum could be reflected by using two methods with the same development trends; for the tests in the range of deformation and failure of surrounding rock in stopes, the maximum errors of BOTDA and the network parallel electric method were 1% and 2%, respectively; the relationship between rock migration and the evolution of different field sources was revealed, and the stress concentration zone, high-resistance zone and severe deformation and failure zone presented a good correspondence. The elastic modulus of the rock stratum was inversely proportional to the deformation level. Furthermore, a field test was carried out on the 1231(1) working face haulage roadway of a mine in Huainan city. Based on the distribution characteristics of the strain field and the geoelectric field, the mining-induced deformation and failure zone of the rock surrounding the roadway were quantitatively delineated. The results showed that “optic-electric” monitoring improved the interpretation accuracy of the anomaly zone and that the test system can quantitatively divide the zones of fracture, plasticity, elasticity and original stress in the surrounding rock, with diffusion radii of 6 m, 18 m, 55 m and > 55 m, respectively. The stratum migration mechanism of the simulation test was further verified and indicated that the test system was scientific and generally widely applicable. The results provide a useful reference for the application of the “optic-electric” method in the monitoring of surrounding rock, which reveals geological disaster information under mining conditions and provides technical guidance for the precise mining of coal and its associated resources. Modern information technology should be deeply integrated at a later stage, and an Internet + “optic-electric” field monitoring method should be developed to further integrate intelligent prevention and control of geological disaster.