Optimization and Practice for Partition Pressure Relief of Deep Mining Roadway Using Empty-Hole and Deep-Hole Blasting to Weaken Coal

Table 3

Multifactor and indexes of orthogonal simulation test.

Pressure relief parameter				Index ()
(mm)	(m)	(m)	(°)	(1) Peak stress position (); (2) stress in the near field (); (3) deformation of roadsides ()
Diameter	Length	Spacing	Elevation angle
90, 100, 110, 120	12, 15, 18, 20	1, 2, 3, 4	0, 5, 10, 15

Note: based on the theoretical calculation of the abutment pressure of the roadsides without pressure relief, it is obtained that the peak stress is at 6.5 m from the roadsides; therefore, the stress at 6.5 m is determined as .