Difference Analysis of Disaster Types and Grading Control Technologies for Risk of Caving of Coal Roadway Roof

Figure 1

Types of disasters due to the caving of the roof of a roadway: (a) examples of caving caused by local block falling between anchor bolts (cables) and a cross-sectional block falling; (b) examples of roof caving induced by an inferior combination of strata of composite layered roofs; (c) examples of caving in a butterfly-shaped plastic zone; (d) an example of caving accident of a loose and fractured roof owing to improper support for small implicit faults.

(a)

(b)

(c)

(d)