Blast-Casting Mechanism and Parameter Optimization of a Benched Deep-Hole in an Opencast Coal Mine

Table 5

Relevant calculation parameters.

Item		Symbol	Value	Unit
Rock parameters	Rock density	ρm	2.24 × 10^3	kg/m^3
	Poisson’s ratio	μ	0.22	—
	Elastic longitudinal wave velocity in rocks	Cp	2406	m/s
	Rock compressive strength	σc	17.5	MPa
	Rock tensile strength	σT	1.75	MPa
	Rock constant	a′	520	—
	Rock constant	b′	1.78	—
Explosive parameters	Density of explosives	ρ0	850	kg/m^3
	Detonation velocity of explosives	D	3000	m/s
Blast hole parameters	Radius of blast hole	rb	155	mm
	Dip angle of blast hole	β	75	∘
	Ultradeep length of blast hole	h	2	m
	Stemming length	ld	6	m
	Bench height	H	40	m