Experimental Investigation on the Release Rule of the Gas Expansion Potential of Loaded Water-Filled Soft Coal

Table 2

Calculation of the friction resistance of the piston in different positions.

Position (m)	0.52	0.53	0.56	0.62	0.65	0.66	0.71	0.73	0.75	0.75	0.76
Air pressure (MPa)	0.11	0.12	0.11	0.13	0.14	0.13	0.14	0.14	0.14	0.15	0.16
Static friction (kN)	0.56	0.59	0.56	0.66	0.68	0.65	0.71	0.71	0.73	0.77	0.80
Dynamic friction (kN)	0.45	0.47	0.45	0.53	0.55	0.52	0.57	0.57	0.58	0.62	0.64