Theoretical Analysis of Damaged Width & Instability Mechanism of Rib Pillar in Open-Pit Highwall Mining

Table 1

Physical and mechanical parameters of coal-rock [9].

Rock strata	Burial depth (m)	Internal frication angle φ (°)	Poisson’s ration (μ)	Density γ (kN·m^−3)	Cohesive force c (MPa)
Surface soil	30	12	0.42	19.6	0.085
Weathered sandstone	44	38	0.36	23.0	2.5
Sandstone	74	39	0.32	23.8	3.0
Mudstone	98	38	0.34	24.9	2.0
Siltstone	110	36	0.32	23.2	3.5
Sandstone	122	40	0.30	23.8	4.0
Coal seam	125	36	0.38	14.4	1.62
Shale	140	42	0.33	24.5	3.8
Siltstone	155	38	0.32	26.0	5.0