Open Shield

Excavation: The open shield TBMs perform the excavation by classical means installed in the front part of the Shield, those can be an excavator boom, a roadheader or a pneumatic hammer.

Advance: Most open shield TBMs are used with reinforced pipe lining which implies that the advance consist on jacking from the launching shaft with hydraulic cylinders. With this method the tunnel moves forward all its length during the advance process so that the pushing forces are transmitted from the jacking frame to the shield throughout all the installed pipes. Also segmental lining can be used with this kind of TBM only the machine is moving during the process because the segments remains on the same definitive position once they are installed therefore the machine pushes against the last ring installed for the advance.

Material extraction: The extraction of the material from the excavation is dry. The material once retired form the tunnel face, falls into a chamber with an conveyor belt or screw conveyor which pours the material into a wagon, allowing the transport of the material out of the tunnel.

Application: Soft ground, heterogeneous ground and rocks up to 80 MPa in areas with no groundwater presence.