Tunnel construction by means of road headers
Performing underground mining in solid and standing ground the stage face method is used. In this case The face is opened for full section in two stages and after that the permanent lining is raised. Mining works are performed by means of heavy-duty mechanical appliances.
Roadheading tunnel construction technology with artificial production of ground is used in wide range of rocks.
In ground with coefficient of resistance f=6 according to Protodiakonov's scale it is possible to use lower stage method when ground in the upper part is headed 30-50 meters advanced as opposed to lower part. The ground in top and bottom faces is cut by means of tunnel boring machines (TBM) of selective action. In this case two independent faces are organized; there are TBM and devices for loading and transportation of excavated ground in each face.
TBM is equipped with mechanized working attachment for ground cutting, bucket-device system and conveyers which allow removing ground from the place and deliver it to the hauling unit. Ground transportation, temporary lining installation and formwork is performed on the analogy of mining method.
Using TBM instead of drill-and-blast method for tunneling prevents destabilization of rock mass due to decreased dynamic force. Moreover, the risk of falls and ground subsidence is minimized. TBM provides creating sharp tunnel outline with minimum excavation that results in decreasing of loading and transport operations and concrete consumption for formwork in comparison with drill-and-blast method.