Table 5 Experimental design for four-factor three-level response surface analysis.

From: Multifactor analysis and dominant factor identification for coal seam gas drainage borehole instability

Factor

Level

āˆ’Ā 1

0

1

A

Confining pressure

6

9

12

B

Gas pressure

1.0

1.6

2.2

C

Temperature

25

40

55

D

Support material

None

PE

PP

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