Arch Engineers Ltd. was engaged to design an urgent recovery plan for a TBM drill head that became stuck approximately 40 meters from its intended exit pit beneath the Clearwater River. This challenging operation required innovative engineering and rapid deployment to address significant project constraints, including a depth of over 10 meters below grade and 7.5 meters below the river water level.
The urgency of the recovery was driven by the potential for the drill head to become permanently fixed under the constantly shifting riverbed, jeopardizing the project schedule and long-term feasibility of the crossing. Initial investigations revealed that a massive, unvisualized boulder was the primary obstruction, necessitating a highly adaptable recovery strategy.
To meet these challenges, Arch Engineers developed a flexible shoring design that allowed real-time modifications by field engineers as recovery operations progressed through four defined stages. This approach ensured that excavation and stabilization measures could be adjusted to the evolving conditions around the TBM head, accommodating the unknown size and position of the obstruction.
The recovery plan incorporated advanced geotechnical modeling and a robust shoring system capable of withstanding hydrostatic pressures and the dynamic nature of the riverbed. Arch’s ability to balance rapid execution with precise engineering ensured the successful retrieval of the TBM drill head, minimizing delays and preventing further complications. This project highlighted Arch Engineers’ expertise in delivering innovative, adaptive solutions under extreme time and environmental constraints.