Since its first project in the 1980s, a Lovat 126 inch (3.2m) TBM has been working continuously in Edmonton on various tunnelling projects.

Recently, the City of Edmonton’s tunnel group within the Drainage Design and Construction department and manufacturer Lovsuns refurbished the open mode TBM.

It was re-designed to integrate a muck ring, pressure leaving gates, and a mixed face cutting head to bore in varying soft grounds, among other upgrades.

The TBM launched in May for the South Edmonton Sanitary Sewer Tunnel Project (SESS), Section SW4. It’s one of four machines currently working underground in Edmonton, on projects constructed by the city’s own in-house tunnelling group.

The Drainage Services equipment team started refurbishing TBMs internally almost two years ago, and their first TBM job saved the city CAD 400,000 (USD 304,000). Since completing that TBM they’ve done refurbishment work for a total of four machines.

SW4 begins at the end of an existing tunnel and as of this fall some 200m of the tunnel drive has been completed, says Darsh Nawaratna general supervisor, equipment (trades and shops) with the City of Edmonton. The length of tunnel is 1,528m and there are two intermediate shafts for ventilation and safety purposes during construction and for future sewer maintenance. The drive will be completed by the end of next year.

Refurbishment work took place in Edmoton except for improvements to the cutter head, which Lovsuns upgraded. Dating back to the 1980s, the manufacuturer modernized cutting tools according to the project’s geotechnical requirements and to create a more versatile TBM, says Sanjay Birbal, sales and parts refurbishment manager for Lovsuns.

“Previously the cutting head had no scrapers and an old style fishplate or centre cutter, and old spade gauge teeth,” he explains.

“We added a full face of scrappers, new conical gauge and spade tools and three modern, replaceable ripper teeth on the gauge, positioned on the outer end of the spokes.”

He adds, “Since TBM launch in May, the TBM has been continuously mining with no issues and no cutting tool changes.”

The city also has two TBMs deployed for the Edmonton Downtown Intensification project, which concerns stormwater. The total project length is 2,160m and the tunnelling group is using 100” (2.5m) and 102" outside diameter machines for this project and expects to complete the work by the end of next year.

The fourth, another 100" machine, is boring the NC 2&3, which is part of the North Edmonton Sanitary Trunk or NEST. “We have already started to do the first portion of this project, 385m, and the second leg of that project is going to be 2,300m long,” Nawaratna reports.

All four of the tunnels under construction start from and finish at shafts lined with rib and lagging. They are lined with precast concrete.

The City of Edmonton owns six TBMs with diameters ranging from 100 inches to 159 inches (4m). The tunnelling group says the reliability of these six machines will play a key role in successfully completing city’s drainage tunnels—a city in which particular areas are seeing rapid population growth.

As of April, the city's population has increased by more than 20,000 people since 2014, the city reports. Looking specifically to the areas served by the SESS a report by ISL Engineering found that population is expected to grow from approximately 25,000 in 2010 to at least 90,000 and possibly closer to 130,000 in 2025. ISL was retained by the City of Edmonton to update the implementation plan for the system, in addition to being the prime consultant to the city with SMA Consulting to provide value engineering and risk assessment services.

In addition to work for the projects underway the tunnelling group began moving into a new 50,000sqf (4,650sq.m) facility in spring 2014. TBM refurbishment work area comprises some 16,400sqf (1,500sq.m), with the rest of the shop dedicated to welding, general mechanics, electrical, a part store and a TBM. As of this April, the move is complete. Edmonton has five full time TBM technicians and one TBM hydraulic specialist. There are also four electricians, eight welders and six heavy-duty mechanics for TBM refurbishment works and other tunnel construction support services.

All Photos: Courtesy Of City Of Edmonton