Mechanism and Procedure of Repeated Borehole Drilling Using Wall Protection and a Soft Structure to Prevent Rockburst: A Case Study

Table 1

Mechanical parameters of the coal and rock used in the numerical model.

Rock strata	Thickness (m)	Density (kg/m^3)	Bulk modulus (GPa)	Shear modulus (GPa)	Cohesion (MPa)	Friction angle (°)
Conglomerate	5	2440	3.06	1.66	2.1	34
Fine sandstone	20	2540	4.5	2.8	2.5	23.25
Carbon mudstone	2	2600	4.2	0.47	3.5	32
Coal	12	1350	0.433	0.2	7.0	33
Fine sandstone	3	2570	1.01	0.70	2.6	26
Mudstone	40	2450	2.82	0.57	3.5	32