LTL Completes Remote Culvert Project in Ontario

By TBM News July 26, 2017

At the end of March, LTL Directional Drilling Ltd. of Shuniah, ON completed a 280-lf, 86-in. OD steel casing culvert with an Akkerman Series II 720 TBM and Tunnel Boring System. The TBM system was used in a remote location on the Camp Creek Culvert project under Highway 627, in Marathon, near Huron Bay, Ontario. The project is owned by The Ministry of Transportation.

Highway 627 is the only access road in the region, so during construction one lane of traffic had to be maintained at all times. The new culvert was installed along the embankments on either side of the highway, with 70-ft of cover above the pipe to the roadway. The culvert that was being replaced was prone to washout at the inlet and outlet points, and was buckling and rusting throughout and below its invert. The project goal was to extend the new culvert further outward along the embankments to integrate proper erosion control.

The contractor selected a closed-face cutterhead for the Series II 720 TBM to prevent subsidence of the silt and sandy ground into the TBM interior. They combined the TBM with a Tunneling Boring System including a 5200 Pump Unit for hydraulic jacking and TBM supply functions with 400 tons of thrust capacity, a thrust yoke and several sizes of skid base to accommodate the 40-ft steel casing, a 1548 Haul Unit for soil transportation and a EH2250 Bentonite Pump to lubricate the outside of the pipe.

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The precarious nature of the weather created challenges at the onset of the project. During the three weeks that the contractor was on-site, the temperatures varied from a low of -31 degrees F to a high of 53 degrees F. An early thaw caused delays on the construction of the concrete launch shaft and reaction block. Just when everything dried out well enough to construct the shaft to launch the TBM, the region experienced extreme cold temperatures causing the moisture in the ground to suddenly freeze then thaw once again a few days later.

Wet flowing ground created immense friction around the first 40-ft length pipe and required the crew to rethink its strategy. Their solution was to add advanced jacking tonnage to the pipe string with Intermediate Jacking Stations (IJS) positioned between each pipe joint and 40 lubrication ports throughout, supplementing the pipe string with an additional 495 tons per IJS adding an extra 2,970 tons. The method proved to be a good decision and enabled crews to complete the replacement culvert within just two weeks.