CASE STUDIES
PROJECT TYPE
Equipment Rescue
LOCATION
British Columbia, Canada
LENGTH / HOLE DIAMETER
DIVISIONS
The Tunneling Company
The Tunneling Company was contracted to rescue a Microtunnel Boring Machine (MTBM), which had become immobilized at a depth of 24 meters — approximately 100 meters short of its intended exit point. To retrieve the stuck machine, The Tunneling Company mobilized a Hydro Hammer alongside the world’s largest earth boring machine: the American Augers 84/96-1.8. Using this powerful equipment, crews installed a 96-inch steel casing over the immobilized MTBM for retrieval.
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To compensate for positional variations within the 20-meter-long MTBM, The Tunneling Company selected a casing entry position and angle that accommodated a slight grade change during installation. This approach ensured the casing remained concentric with the stuck MTBM, allowing for its safe removal.
Contingency measures were established to maintain alignment and grade, including periodic clean-outs for survey verification and options to telescope down to 84-inch or 72-inch casings if minor corrections were required. During installation, crews encountered perched water within a layer of silt and sand. As a result, cleanout and survey activities near the casing face became increasingly difficult.
With 40 meters of casing installed, survey data indicated a grade correction was necessary. To address this, shims were welded inside the casing, allowing for a slight adjustment of the casing's entry angle.
Due to schedule urgency and uncertainties regarding the accuracy of pipe ramming in wet silty conditions, The Tunneling Company also constructed a segmental shaft to a depth of 7 meters in front of the MTBM’s position. This provided an additional option to hand-tunnel from the shaft if the pipe ramming method failed.
The rescue casing successfully intersected the immobilized equipment, and all three sections of the MTBM were extracted through the 84-inch casing. After the MTBM’s removal, crews inserted a 36-inch pipeline through both the pre-existing 42-inch casing and the rescue casing — completing the pipeline installation and tie-in at both ends.
Ultimately, this successful casing intersect and MTBM removal overcame a critical interruption in the client's project. The Tunneling Company’s ability to rapidly mobilize and execute the rescue plan helped avoid further delays, allowing the client to safely accomplish their objective as efficiently as possible.
The rescue casing successfully intersected the immobilized equipment, and all three sections of the MTBM were extracted through the 84-inch casing. After the MTBM’s removal, crews inserted a 36-inch pipeline through both the pre-existing 42-inch casing and the rescue casing — completing the pipeline installation and tie-in at both ends.
Ultimately, this successful casing intersect and MTBM removal overcame a critical interruption in the client's project. The Tunneling Company’s ability to rapidly mobilize and execute the rescue plan helped avoid further delays, allowing the client to safely accomplish their objective as efficiently as possible.
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