This process avoids the need to have a long stretch of open trench for pipe-laying.
Microtunneling includes these steps:
- Microtunnel ShaftExcavate launching and reception shafts at opposite ends of the tunneling drive.
- Hydraulic jacks in the launch shaft push a microtunnel boring machine (MTBM) into the earth.
- Pipes containing slurry water transport excavated spoils to the surface
- Retract the jacks and disconnect slurry lines and control cables.
- Lower a pipe or casing into the shaft and insert it between the jacking frame and the MTBM.
- Reconnect slurry lines and control cables and advance the MTBM another drive.
- Repeat the process until the MTBM reaches the reception shaft.
- Retrieve the MTBM and trailing equipment.
- A closed loop slurry system to transport excavated spoils
- A slurry cleaning system to remove spoils from the slurry water
- A lubrication system to lubricate the exterior of the pipe during installation
- A guidance system to provide line and grade control
- An electrical supply and distribution system to power equipment
- A crane to hoist pipe sections into the jacking shaft
- Trucks and loaders to transport spoils off site
Additionally, the MTBM has inline cameras to relay information to the operator and a target system for guidance control. Precise control of line and grade is accomplished using the guidance system and steering jacks to locate and steer the MTBM during a microtunneling drive.
The guidance system usually consists of a reference laser mounted in the jacking shaft, which transmits a beam onto a target mounted inside the articulated section of the MTBM. This and other operational information is transmitted through wire cables to a control cabin located on the surface.