Determination and Application of Reasonable Levels for Highly Directional Long Boreholes in Deep Outburst Coal Seams

Table 2

Physical and mechanical parameters of rock formations.

Lithologic	Apparent density/kg·m^3	Cohesion/MPa	Bulk modulus/GPa	Shear modulus/GPa	Internal friction angle/°	Tensile strength/MPa
Coal seam	1470	2.4	1.45	0.74	18	1.43
Medium sandstone	2432	6.8	4.89	2.13	35	2.7
Silty sandstone	2421	4.8	3.69	3.24	38	2.00
Mudstone	2422	4.8	3.69	3.24	38	2.00
Fine sandstone	2454	4.3	2.32	1.82	29	1.53