Numerical Simulation on the Evolution of Mining-Induced Fracture Network in a Coal Seam and Its Overburden under the Top Coal Caving Method

Table 2

Physical and mechanical properties of the strata.

Strata	Density (kg/m^3)	Bulk modulus (GPa)	Shear modulus (GPa)	Cohesion (MPa)	Friction angle (°)	Tensile strength (MPa)
Fine sandstone	2800	65.0	54.4	14.2	54	9.3
Medium sandstone	2700	44.1	41.6	12.3	48	5.2
Siltstone	2736	54.4	51.2	11.8	50	5.41
Pebbly sandstone	2578	36.5	32.2	7.55	40	4.27
Coal seam	1460	2.7	1.2	2.65	30	2.39
Mudstone	2500	26.5	21.2	4.57	35	2.57
Upper strata	2500	26.5	21.2	4.57	35	2.57