A.5m B.10m C.15m D.20m
A.2°-5° B.3°-5° C.5°-8° D.5°-10°
A.0.6Ho(Ho為平均開采深度) B.0.7Ho(Ho為平均開采深度) C.0.8Ho(Ho為平均開采深度) D.0.9Ho(Ho為平均開采深度)