Full-space multi-parameter cooperative monitoring of failure hierarchy characteristics of mining coal seam floor

In order to fully obtain the failure evolution and hierarchical characteristics of mining coal seam floor, the borehole water injection test method (point), the borehole peeping method (point), the borehole distributed optical fiber monitoring method (line), and the transient electromagnetic method (plane) were used to construct a full-space point-line-surface collaborative monitoring mode of the coal seam floor;according to the mining failure degree of coal seam floor, from the multi-parameter perspectives of fracture water conductivity, tensile shear strain, and physical properties of mining rock, the water-conducting damage zone of the coal seam floor in the lower three zones is divided into water conduction failure zone, stress-strain zone and physical property difference zone; Taking No.9 coal working face in Pingshuo Mining Area as the measured object, the full space of the mining coal seam floor, dynamic and static, multi-level deformation and failure characteristics of mining coal seam floor are obtained. The results show that point-line-plane multi-parameter collaborative monitoring method can realize point-line-plane dynamic and dynamic monitoring in monitoring space. The monitoring content can meet the requirements of obtaining the characteristics of fracture development, water conductivity, strain deformation and physical properties directly or indirectly. The borehole water injection test method and the borehole peeping method are the methods to directly monitor the development characteristics of fractures, A water conduction failure zone of 21.75 m was obtained using distributed optical fiber monitoring method to dynamically monitor fracture development characteristics.When advancing to the vicinity of the borehole, the local rock mass of the bottom plate appeared tensile failure. The working face pushes through the borehole for a distance, and the tensile degree of the rock mass of the bottom plate continues to increase, but the depth of failure remains basically stable and the measured stress-strain zone was 25.15m. The transient electromagnetic method can be used to compare and obtain the physical properties of rock mass before and after mining.The analysis shows that the physical property difference zone is 22-27 m, which well verifies the hierarchical division characteristics of the floor mining damage.