Trenchless Installation of Concrete Pressure Pipes for Water and Wastewater Applications

As both urban and rural development continues to expand across North America and existing infrastructure continues to age, asset owners are on the lookout for unique ways to keep up with population growth and service this demand through the addition of new pipelines while upgrading existing systems utilizing a variety of installation techniques. Trenchless installation of pipelines in the water and wastewater industry has become a popular way to expedite this work while minimizing disruption to the public. Traditionally, two-pass trenchless construction methods have been used, where the tunnel is dug or bored and the carrier pipe is then installed within the tunnel. Various methods of tunnel support such as rib and lagging, segmental tunnel liners, and microtunnel pipe have been used across North America. Depending on the tunneling method that is used, the carrier pipe can be installed in multiple ways, such as the use of pipe spacers, a rail system, pipe car, or raised mortar-coated collars. Microtunneling has become increasingly popular over the past decade to install pipelines of various sizes (typically up to 3.0 m in diameter) with runs in excess of 1,000 m having been installed throughout North America. The popularity of this technique continues to grow as it can help cut down on both construction time and cost when compared to other installation methods. One of the benefits of microtunneling that has contributed to its growth in popularity is that the pipes have the ability to act both as the tunnel support and as the carrier pipe, therefore not requiring a traditional two-pass tunneling method in many cases. This technical paper will review the critical design elements and installation of concrete pressure pipes for both single and two-pass installations of trenchless pipelines intended for pressurized and gravity applications, as well as the benefits of tunneling. The audience will be left with an understanding of how exactly trenchless techniques can be utilized to install pipelines, and a summary of example projects will be reviewed to give the reader a better appreciation for this type of installation method and when it should be used.