Table 1 The buffering and pressure adjustment tests for the surrounding rock.

With/without airbag

With

With

Without

Airbag thickness (mm)

30

30

–

Internal gas

Air

Air

–

Test temperature

Air temperature – 20 °C, boundary temperature of surrounding rock 6 °C

Air temperature –30 °C, boundary temperature of surrounding rock 3 °C

Surrounding rock water content

Saturated state

Initial pressure (kPa)

18

13

8

13

–

Pressure adjustment time interval (h)

–

15

–