Swelling Pressure of Double-Expansive Material and Its Active Support Effect for Coal Seam Gas Drainage Borehole

Table 1

Constraint stiffness in the four tests.

Test no.	δ (mm)	rb (mm)	Sr (MPa·m^2)	Sa (MPa·m^2)
1	2	7	41.2	126.8
2	3	7	61.8	126.8
3	4	7	82.4	126.8
4	5	7	103	126.8

Radius of the bolt.