Hollow Effect of Ground Vibration Induced by Electronic Detonator in Shallow Tunnel

Table 1

Blasting parameters of the middle bench.

Blasting event	Blasthole type	Blasthole number	Blasthole length (m)	Blasthole spacing (m)	Blasthole diameter (mm)	Charge diameter (mm)	Charge weight per hole (kg)	Delay time (ms)
Middle bench	Easer hole	24	2.2	1.0	42	32	1.1	10
	Periphery hole	10	2.2	0.25	42	32	0.5	10
	Bottom hole	13	2.2	1.0	42	32	1.1	10