Tunnel boring technology digs deeper

Jeff Petersen, chairman of UCA SME summarized the developments in the field of tunneling before discussing the Kemano Backup Tunnel Project last Wednesday. According to Petersen, the underground construction industry is expanding rapidly with some companies experiencing 20% growth in employee size each year. The work involved in underground construction is so complex that individuals from a large variety of fields and degrees can be successful in the industry.

With current developments in technology, enormous tunneling projects in high risk areas have been successful. One example of this success was the project that expanded the New York subway system. In order to expand the subway, tunneling had to be done under some of the most expensive buildings in the world. Not only was there a risk of building collapse, but the tunnelling was also done with extreme care to avoid disturbing pre-existing tunnels. Enormous caverns as large as 1400 feet long had to be blasted within feet of old structures.

Tunnel boring machines are quite the rave for softer rock tunneling. These five story high machines look like particle accelerators connected to a long steel worm. Tunnel boring machines are able to carve the entire tunnel and line it, which dramatically decreases human labor required to operate machinery and construction time. Traditional methods still exist to tunnel in hard areas.

In terms of projects, the industry is growing fastest in the United States due to the need for expanded water and sewer systems. These projects arose from the need for cities to meet the CSO compliance for the Midwest. Currently over 700 cities have CSO initiatives, primarily to increase storage. Here, sewer tunnels act primarily as big storage tanks so that the current processing utilities can continue to process waste without being flooded. Additionally, in Europe and on the coasts of the United States, many opportunities exist in light and heavy rail development.

Big tunneling construction companies understand that training an employee to have the necessary degree of proficiency in the industry requires 10 to 12 years. Because of the need to meet the demands of the expanding market, some of these big companies and societies are providing students access to conferences and training opportunities at very low costs. For example, the RETC (Rapid Excavation and Tunneling Conference) is free for a group of Mines students selected to represent the school. (Applications for this opportunity are due April 15. Scholarships are also available for education expenses sponsored by the conference.)

Petersen also explained that those new to the industry are often trained during the seasons construction cannot be performed on projects. For example, the Kemano Backup Tunnel Project is in the mountains. The base of the mountain is only accessible by boat and helicopter, and getting materials and personnel to the site requires a week and a half. Because the area gets feet of snow on a regular basis during the winter, project members use the time they cannot be on site to perform test installations and become experts in the techniques required for successful installation of the tunnel. Logistics and planning are key due to the time and location constraints. Additionally, when construction occurs, the existing tunnels must be temporarily shut down. For each hour a tunnel is not operating due to close proximity boring, the utility losses $100,000 and runs the risk that construction will cause the collapse of the existing tunnel. Such construction sites are too high profile for new employees to gain much experience, which is why having them trained in the off season is so important.

Although the demand for tunnel construction far surpases the current industry capacity, Petersen expressed optimism and excitement about the challenges ahead, claiming, “We must see challenge as an opportunity to overcome.”