Microtunneling & Pipe Jacking

A Sophisticated Technology with High Precision – Conventional Pipe Jacking is a method of installing prefabricated pipe sections by pushing or jacking the pipe behind a tunnel boring machine or a number of other tunnel excavation methods. Microtunneling is an unmanned, remotely controlled, pipeline construction method for installing casing pipe or a carrier pipe (as in one-pass systems) underneath natural as well as man-made obstacles in a wide range of geotechnical conditions. Simultaneously, pipe sections are jacked in behind the microtunneling boring machine (MTBM), while maintaining very close tolerances to line and grade from the drive shaft to the reception shaft.

A key feature of microtunneling is its versatility to protect a tunnel face using slurry pressure, which makes it a trenchless construction method of choice especially when traversing underneath high water tables and unstable grounds.

Port_Manatee_ProjectMicrotunneling Operation – Key components of a Microtunneling operation includes the MTBM, which incorporates a cutter head, an automated spoils transportation system, and a guidance and remote control system. There is also the Pipe Jacking system which enables direct installation of the product pipe behind the MTBM by the forward thrusting action of the jacks.

Finally, the Product Pipe which should be able to withstand design jacking forces without buckling, and subsequent internal working pressures if applicable. Most importantly, the casing or product pipe should have a proven joint that does not reduce installation productivity. The jacked pipe can be a two-pass system (casing pipe and carrier pipe), or a one-pass system (single pipe acts as both casing and carrier pipe).

Northwest Pipe Company’s proprietary interference fit Permalok® interlocking push-joint steel casing pipe system has been the product pipe of choice for microtunneling for nearly twenty years, during which more than 2 million feet of the T-5 and T-7 type joints have been installed throughout North America.

The primary benefits offered by Permalok® include expeditious joint assembly in the field compared to time consuming butt-welding of traditional steel casing pipe, resulting in excellent construction productivity and thus savings, and unequaled precision and accuracy provided by a joint of consistent quality and integrity. Also available through Northwest Pipe Company is beveled-by-square edge joints for traditional butt-welded casing pipe applications if specified.