Application of Distributed Optical Fiber Technology for Coal Bump Prevention

Table 1

Characteristics of borehole development.

Stage	Deformational behaviour	Observation	Duration
Crack development	Small strain, increasing of radius	Smooth hole wall	0∼72 h
Limited equilibrium	Slow increase of strain and radius	Coarse hole wall but no collapse	72∼190 h
Collapse	Linear increase of strain and radius	Collapse of the hole	190∼402 h
Compaction	Slow increase of strain but radius does not increase	Hole fulfilled by broken coal	>402 h