(1) Identify the size and shape of the goaf, including the volume of the goaf, the projected area of ​​the empty area, the shape of the goaf, the connectivity of the goaf (independent goaf or gob), and the height of the goaf And length to width ratio;
(2) Identifying the water filling situation in the goaf;
(3) Identifying the physical and mechanical properties of ore and rock around the goaf, and investigating the lithology should pay special attention to the brittleness and plasticity of the rock;
(4) Find out the length of the goaf;
(5) Identify the changes in the size of the goaf, including the method and annual processing capacity of the goaf, and the quantity and volume of the newly added gobs;
(6) Investigate the occurrence of caving in goaf, including gradual retreat or staged large-scale retreat, whether the surface collapses and sinks, and analysis of historical ground pressure accidents;
(7) Pumping and drainage near the goaf and its impact on the stability of the goaf.
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