Evaluation of Water Retention Capacity of Bulkheads in Underground Coal Mines

Table 2

Connectivity coefficients of water conducting pathway of interface between bulkhead and surrounding rock.

Connectivity coefficient of water conducting pathway m	Type of bulkhead	Length of bulkhead L (m)		LD/L	Water pressure P (MPa)	Pg/Pd	Pressure test stabilization time t (h)
		Main section	Reinforcement section on both sides
8–10	Rectangular/flat	≤2	≤10	<1	≥5	≤1	≤24
5–7	Cylindrical	2–4	10–15	1–1.1	3–5	1.0–1.5	24–28
3–4	Tapered	4–6	15–20	1.1–1.2	2–3	1.5–2	28–32
1–2	Inverted pyramid	≥6	≥20	≥1.2	≤2	≥2	≥32