Shield Tunneling

Excavator shield tunneling is a trenchless method used for larger diameter utility and crossing tunnels. This specialized form of tunneling includes a steerable forward shield with a hood that extends beyond the excavating face for ground stabilization. The material at the face is excavated by a digger arm that is controlled by an operator inside the shield. As the pipe string advances in the pipe jacking mode or propelled by a jacking can in a ring building mode, the leading edge of the shield scarifies the ground while the excavator’s arm moves material onto the conveyor belt for removal. A hydraulically controlled steering joint allows the onboard operator to make line and grade adjustments when dictated by the tunnel laser mounted in the launch shaft.

Mode of Operation

Pipe jacking or two-pass utility tunneling.

Accuracy

Tunnel laser or total station guidance. Suitable for gravity flow installations.

Diameter Range

100-in to 168-in typical

Ground Conditions

Most suitable for non-pressurized ground. Ground conditions that contain obstacles such as wood, fill, boulders, and existing utilities may be considered as access to face for removal is easily achieved.

Safety

Excavator shields contain a forward shield hood, removable sand shelves, and optional hydraulically closeable doors to assist with ground support during excavation.

Drive Lengths

Typical drive lengths range from 50 to 1200-lf. Contact representative to discuss project details.

Shaft size

Shaft size is dependent on mode of operation and pipe length. Pipe jacking projects typically use 40-ft working shaft lengths. Shorter lengths are possible. Consult Akkerman representative for details.