Research Article
Evaluation of Water Retention Capacity of Bulkheads in Underground Coal Mines
Table 6
Connectivity coefficients of water conducting pathway in fractured zone around mine opening in surrounding rock.
| | Connectivity coefficient of water conducting pathway m | Stability of surrounding rock | Thickness of fractured zone LP (cm) | Water pressure (MPa) | Roadway depth B (m) | Type of bulkhead | Properties of surrounding rock |
| | 9–10 | Extremely unstable | ≥300 | ≥7 | ≥5.0 | Rectangular | Hard | | 7–8 | Unstable | 200–300 | 5–7 | 4.0–5.0 | Flat | Hard | | 5–6 | Generally unstable | 150–200 | 3–5 | 3.5–4.0 | Cylindrical | Medium hard | | 3–4 | Fair | 100–150 | 2–3 | 3.0–3.5 | Tapered | Soft | | 2 | Somewhat stable | 40–100 | 1–2 | 2.5–3.0 | Inverted pyramid | Very soft | | 1 | Stable | 0–40 | ≤1 | 2.0–2.5 | Inverted pyramid | Very soft |
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The thickness of the fractured zone is determined by geophysical prospecting or drilling methods.
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