Research Article
Safety Mining Technology of Coal Seams in Weathered Zone Based on Ground J-Type Pregrouting Reinforcement
Figure 4
Movement law of the overburden strata when two hard rocks exist: advancing distances of the working face are (a) 35 m, (b) 45 m, (c) 50 m, and (d) 90 m.
(a) |
(b) |
(c) |
(d) |