Study on multi-parameter monitoring of overburden failure in deep strip old goaf

In view of the movement and deformation of overlying rocks in deep strip old goaf, the main parameters such as fracture development, tensile and compressive strain and rock physical property have been determined. A "point-line-surface-body" multi-parameter monitoring mode for overlying rocks in goaf areas has been constructed using borehole television method, distributed fiber optic sensing method, cross well electrical CT method, and microseismic method. The monitoring model was used to analyze the engineering example, and the comprehensive and multi-level movement and failure characteristics of the overlying rock in the goaf were obtained. It is concluded that the overlying rock fractures are mostly concentrated below 465 m, and a few cavities are located above the collapse zone and coal pillar near the goaf side, and the plastic zone of the coal pillar is about 8 m. Therefore, it is determined that the overlying rock structure in the goaf remains relatively stable for a long time. The results indicate that the "point-line-surface-body" multi-parameter monitoring mode can effectively cover various parameter indicators of the movement and deformation of the overlying rock in the strip goaf in terms of content, and can achieve the full process monitoring of the combination of point (static), line (dynamic), surface (static), and body (dynamic) in time and space. The monitoring results can be mutually verified, and can meet the requirements of monitoring the movement and deformation of the overlying rock in the deep strip goaf.