Direct Steerable Pipe Thrusting (DSPT)

This system is a hybrid of directional drilling and microtunneling that was developed and patented by a private company as the DirectPipe® method. In the system, a slurry microtunneling machine excavates the soil and is steered along the planned alignment. The machine is welded to the front of a continuous steel pipe that advances through the ground at the same time. The thrust to advance the pipe and the microtunneling machine is provided through a pipe gripping system at the launch pit – allowing the pipe to be prepared as a continuous string before installation. The system can install large diameter pipes in a single pass and only a small annular gap is provided around the pipe during installation – which eliminates the possibility of a borehole collapse. The method also limits the major space requirements for site work and installation to only one side of a crossing. If the space on the launch side of the crossing is also partially restricted, it is possible to weld two or more different sections of pipe string together during the installation process.