Vacuum microtunneling case studies in conditions ranging from soft soils to hard rock

Though trenchless technology continues to penetrate the underground utility installation market, one industry continues to depend on the age-old practice of open cut trenching. Small diameter gravity sewer projects, defined as less than 600mm, continue as they have for decades, relatively untouched by the benefits of trenchless technology. These projects are engineered and executed with little change as compared to 40 years ago, with often greater than 90% of the installation being performed by trenchers and excavators. Part of the reason for this is the lack of knowledge in the sewer industry as to the benefits and capabilities of the trenchless methods available. One of the newest trenchless technologies capable of boring small diameter on-grade gravity sewer is the recently introduced AXIS^TM Guided Boring System. Though the design of the system was originally targeted at bores averaging 90 meters in length, diameters of 250-350mm, and in soft soil conditions, those boundaries have since been stretched to include longer bores, larger diameters, and most importantly, a variety of ground conditions. This paper will present project case studies that have been completed with the AXIS system in a variety of ground conditions, from hard rock to below water table saturated ground. Utilizing purpose-designed cutter heads and tooling, the applications for this vacuum microtunneling technology are greater than ever before. Actual projects and specific bores executed by industry leading contractors will be discussed, demonstrating that the installation of small diameter gravity mains can now be accomplished cost effectively with a trenchless technology.