Definition and History
Microtunneling is a process that uses a remotely controlled, guided Microtunnel Boring Machine (MTBM) that provides continuous face (ground and water) support combined with the pipe jacking technique to directly install product pipelines underground in a single pass with limited man access. This process avoids the need to have long stretches of open trench to install pipe, which causes extreme disruption to the community. In the U.S., microtunneling has been used to install pipe from twelve inches to twelve feet in diameter. In the U.S. the definition for microtunneling does not necessarily include a size, but, a method. Microtunneling is currently the most accurate pipeline installation method. Line and grade tolerances within one inch are typically achieved.
Microtunneling was developed by the Japanese in the early 1970’s to install sanitary sewer pipes and replace the use of open/exposed sewers in urban areas without major disruption to the urban community. The first microtunneling project in the U.S. occurred in south Florida in 1984.This was a 600 foot crossing with 72″ pipe under I 95 and the FEC Railroad. Although originally designed for gravity sewer pipe installation, microtunneling installations include a variety of utilities including sewer, water, oil/petroleum, electrical, etc for the underground crossings of highways, railroads, runways, rivers, and environmentally sensitive areas. This process has also been used to install intakes and outfalls for power, water and sewer plants, etc. Microtunneling is also used in the pipe arch technique of supporting large underground openings with an arch or roof made up of small tunnels.