If it need, a layer with 50 mm thickness in roof.

Stone screw with 20 mm diameter and fully injected

At a distance of 2.5 meter, rock bolts with 3 meters length will locally installed, if necessary, the wire mesh will be used too.


Dig a full point, progress at each turn 1 - 1.5 meter and after 20 meter progress the complete maintenance system will be performed.

Rock mass class

2-Good rock RMR = 61 - 80.