Table 2: The mechanic parameters of rocks.

Rock type	Young’s modulus/GPa	Poisson’s ratio	Rock type	Young’s modulus/GPa	Poisson’s ratio
mud stone	2.84	0.28	tight sandstone	7.02	0.21
coal	0.4-0.8	0.22-0.33	limestone	6.74	0.23
fine sandstone	5.82	0.25