Study on the Radial Displacement Law and Permeability Enhancement Effect of Coal Body around Hydraulic Flushing Drilling

Table 3

Drilling effective radius of pressure relief.

Borehole diameter (mm)	Critical position (numerical simulation) (m)	Radial line strain corresponding to critical position (‰)	Critical position (onsite measurement) (m)	Pressure relief area (in diameter) (m)
200	0.91	23.40	0.97	0.91
600	2.59	26.78	1.77	1.77