Impact of longwall mining on slope stability – A case study

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Change of FoS value and size of the slope failure surface with different scenarios of UG operation by 2025_

Slope in 2025	FoS valueSize of the slope failure surface
	Before UG	After UG
		Scenario I	Scenario II	Scenario III
Left slope wall	1.75–2.0	1.75–2.0Increased	1.5–1.75Increased	1.75–2.0-
Right slope wall	>2.5	>2.5-	>2.5-	2.0–2.25Increased

Mechanical properties of rock mass in the studied region [33]_

Type of rock mass	Bulk modulus K (GPa)	Shear modulus G (GPa)	Cohesion c (MPa)	Fiction angle φ (°)	Tensile strength σt (MPa)	Density ρ (kg/m3)
Mudstone	2.31	1.54	1.87	30	1.34	2620
Claystone	2.23	1.34	2.05	26	1.14	2600
Anthracite	2.17	1.36	2.14	27	1.22	1500
Conglomerate	4.76	3.57	3.23	28	2.27	2510
Sandstone	3.91	2.46	3.56	28	1.96	2600

Strength parameters of the fault in the studied region [33]_

Strength parameters	Friction angle (°)	Cohesion (kPa)	Tensile strength (kPa)
Value	12–20	3.4–4.4	0

Hypotheses for calculating thickness of the caved zone_

Author, year	Thickness of caved zone
Peng and Chiang, 1984 [38]	(2–10)t
Bai et al., 1995 [39]	100t/(c1g+c2)
Mazurkiewicz et al., 1997 [40]	t/(kr−1)
Heasley, 2004 [41]	(10–18)t
Biliński, 2005 (simplified) [42]	(nkst)/(0.05Rc0.5+0.02)
Wang et al., 2017 [43]	(3–4)t