Together, we solve the challenges of tomorrow.
LEARN MORE →Underground excavations in Saguenay encompass a specialized branch of geotechnical engineering focused on the safe and efficient creation of subterranean spaces, from utility tunnels and transit corridors to deep foundations and mining infrastructure. This category addresses the full lifecycle of underground construction, including site characterization, structural design, ground support, and long-term monitoring. In a region defined by challenging glacial deposits and sensitive clay formations, the importance of rigorous underground excavation practices cannot be overstated. The integration of advanced geotechnical analysis for soft soil tunnels is critical to mitigating risks such as face instability, excessive settlement, and groundwater intrusion that are prevalent in Saguenay's unique geological context.
Saguenay's subsurface conditions are heavily influenced by the last glacial retreat, which left behind thick sequences of marine and lacustrine clays, notably the sensitive Laflamme Sea clays. These fine-grained soils are prone to quick clay behavior when disturbed, posing significant challenges for any underground work. Additionally, the region features variable bedrock topography, with Precambrian Shield rock often overlain by compressible overburden. The presence of high groundwater tables, particularly in the low-lying areas near the Saguenay River and its tributaries, adds another layer of complexity. These factors demand a meticulous approach to geotechnical design of deep excavations, ensuring that temporary and permanent support systems can withstand both earth and hydrostatic pressures while protecting adjacent infrastructure.
All underground excavation projects in Saguenay must adhere to the stringent requirements of the National Building Code of Canada (NBC) and the Quebec Construction Code, with specific references to CAN/CSA standards for deep foundations and earthworks. Provincial regulations, guided by the Ordre des ingénieurs du Québec (OIQ) and the Ministère des Transports du Québec (MTQ), mandate comprehensive geotechnical investigations and design reports for any excavation exceeding a certain depth or proximity to public rights-of-way. The Canadian Foundation Engineering Manual provides essential guidelines for empirical design methods, while the Quebec Environment Quality Act governs groundwater control and dewatering permits. Compliance with these frameworks is non-negotiable to ensure public safety and environmental protection.
The practical applications of underground excavation engineering in Saguenay are diverse. Major infrastructure projects, such as the installation of combined sewer overflow tunnels for the city's aging drainage network, rely on these principles. The region's hydroelectric sector often requires underground penstocks and powerhouse caverns, while the mining industry demands shafts, ramps, and ore passes. Urban development, including the construction of underground parking structures and building basements in the Jonquière and Chicoutimi boroughs, necessitates precise excavation support. Each project type, whether a microtunnel for fiber optic installation or a large-scale transit bore, depends on a thorough understanding of how the local ground will behave during and after excavation.
The main risks stem from the region's sensitive marine clays, which can knowledge sudden loss of strength (quick clay landslides) when disturbed by excavation. High groundwater tables in valley bottoms create significant hydrostatic pressure and potential for base heave or piping. In rock, the irregular bedrock surface and fractured zones can lead to water inflows and instability, making thorough pre-construction investigation essential for risk mitigation.
Underground excavations are primarily governed by the National Building Code of Canada (NBC) and the Quebec Construction Code. Key referenced standards include CAN/CSA-S6 for highway structures and CAN/CSA-A23.3 for concrete design. The Canadian Foundation Engineering Manual provides essential design methodologies, while provincial bodies like the OIQ enforce professional practice standards and the MTQ specifies requirements for public infrastructure projects.
Mixed-face conditions, where the tunnel or excavation face encounters both soft soil and hard rock simultaneously, demand highly adaptable construction techniques. This scenario is common in Saguenay's transition zones between the clayey overburden and the Precambrian Shield. It often requires switching from soft-ground tunneling methods to drill-and-blast or roadheader excavation, complicating ground support design and requiring continuous face mapping to maintain stability and worker safety.
The process begins with a comprehensive geotechnical investigation and a design report sealed by an OIQ-registered engineer. This package is submitted to the relevant municipal authority for a building or excavation permit. Dewatering activities require a certificate of authorization from the Quebec Ministry of the Environment (MELCCFP). For projects near provincial roads or watercourses, additional approvals from the MTQ or the Saguenay Port Authority may be necessary, involving detailed impact assessments.
We serve projects across Saguenay and its metropolitan area.