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.
Case Studies
Blacks Run Interceptor Division 1B Replacement
The Blacks Run Interceptor – Division 1B –Replacement project scope included 3,700-lf. of 48-in. sanitary sewer installed by open-cut and trenchless methods.
A 200-lf. section that crossed under Stone Spring Road requiring a tunnel boring machine to maintain traffic on a busy arterial roadway.
