Selection of Compatible Coal Seam for Methane Drainage Operation Based on Uncertain Geological Conditions: A Hybrid Fuzzy Approach

Table 6

The quantitative and qualitative classification of geological criteria affecting MDA.

Criteria	Quantitative and qualitative classification of criteria
Depth of seam (m)	1–100 very shallow	100–200 shallow	200–400 nearly deep	400–600 deep	600 < very deep
Thickness of seam (m)	<0.5 very thin	0.5–4.5 thin	4.6–6 nearly thick	6–30 thick	30 < very thick
Cleats condition (joint/m)	0–3 very few	3–10 few	10–15 moderate	15–20 numerous	20 < very numerous
Uniformity of seam	0–0.5 very uniform	0.5–1.3 uniform	1.3–2 nearly uniform	2–2.8 nonuniform	2.8 < quite nonuniform
Gas content (m^3/ton)	0–5 very low gaseous	5–10 low gaseous	10–15 moderate gaseous	15–20 gaseous	20 < very gaseous
Roof quality (MPa)	5–40 very weak	40–100 weak	100–200 moderate	200–300 strong	300 < very strong
Underground water condition (m^3/min)	0–35 dry	35–70 wet	70–105 very wet	105–140 hydrous	140 < very hydrous
Permeability (mDarcy)	0–5 very little	5–15 little	15–30 moderate	30–45 very much	45 < much