Sound ground. Sound decisions.
LEARN MOREGround improvement encompasses a critical suite of geotechnical techniques designed to enhance the engineering properties of soil and rock masses, ensuring they can safely support structural loads and resist seismic forces. In St. John's, Newfoundland, this category covers everything from densifying loose, granular deposits to reinforcing soft, compressible clays and silts. The importance of these methods cannot be overstated in a region where challenging native soils are the norm, and the consequences of inadequate foundation support range from excessive settlement to catastrophic bearing capacity failure. By modifying the ground, we mitigate these risks, allowing for safe construction on sites that would otherwise be deemed unsuitable, directly impacting the longevity and safety of infrastructure across the Avalon Peninsula.
The geological landscape of St. John's is dominated by the legacy of glaciation, leaving behind a complex and highly variable stratigraphy. Bedrock, typically part of the Precambrian Signal Hill Group, is often overlain by a discontinuous mantle of glacial till, which can be dense but is frequently interspersed with pockets of loose, water-bearing sands and gravels. More problematic are the extensive deposits of marine clays and silts, particularly in lower-lying areas near the harbour and Waterford Valley. These fine-grained soils are often normally consolidated or slightly overconsolidated, making them highly susceptible to long-term settlement under load. Additionally, the region's high water table and proximity to the North Atlantic introduce challenges with groundwater management and the potential for soil liquefaction during a seismic event, making targeted ground improvement a prerequisite for resilient design.
Geotechnical practice in Newfoundland and Labrador is governed by the national standard CAN/CSA-A23.3 for concrete design and the Canadian Foundation Engineering Manual (CFEM), which provides the overarching principles for bearing capacity and settlement analysis. Crucially, for seismic considerations, the National Building Code of Canada (NBCC) is enforced, with St. John's assigned a specific seismic hazard value that mandates liquefaction assessment for certain site classes. While no provincial code explicitly dictates a single ground improvement method, the professional practice standard requires that all designs meet the limit states outlined in the NBCC and CFEM. This means a rigorous site investigation per CAN/CSA-S472 is non-negotiable before designing a ground improvement program, ensuring the chosen solution, such as stone column design, is validated for the site-specific soil conditions and seismic demand.
The types of projects in St. John's that routinely require ground improvement are diverse. Commercial developments on the infilled lands of the downtown core and institutional buildings expanding Memorial University's campus often encounter undocumented fill or sensitive marine clays, demanding solutions to control differential settlement. Heavy industrial projects, such as tank farms and warehouses in the Donovans Industrial Park, frequently rely on vibrocompaction design to densify loose, granular fills and native sands, increasing bearing capacity and preventing dynamic settlement from vibrating equipment. Transportation infrastructure, including highway overpasses and port facility expansions, also depends on these techniques to stabilize embankments and ensure the long-term performance of critical logistics routes in the region's harsh climate.
Ground improvement in St. John's primarily targets settlement of soft marine clays and silts common in lower-lying areas, bearing capacity failure in loose or undocumented fills, and the risk of soil liquefaction during an earthquake. The region's high water table and complex glacial stratigraphy make these hazards particularly acute, requiring engineered solutions to ensure stable, long-term foundation performance.
The necessity is determined through a comprehensive geotechnical investigation following CAN/CSA-S472. If the report reveals loose sands, soft clays, uncontrolled fill, or a high groundwater table that could lead to excessive settlement, low bearing capacity, or liquefaction under the seismic loads specified by the National Building Code of Canada, then ground improvement is likely required.
Ground improvement treats the soil mass in place to enhance its properties, creating an improved ground that can support shallow foundations. Deep foundations, like piles, bypass the weak soil entirely to transfer loads to bedrock or a deeper competent stratum. In St. John's, ground improvement is often preferred when the weak zone is shallow to moderate in depth, as it can be more economical and faster for supporting large, uniformly loaded structures like floor slabs.
The NBCC defines the seismic hazard for St. John's and classifies sites based on soil stiffness. For sites with soft clays or loose sands (Site Class D or E), the code may increase design seismic forces and requires a liquefaction assessment. A ground improvement design must demonstrate that the treated ground meets the performance criteria for the intended site class, effectively mitigating the code-mandated hazards.
We serve projects in St. Johns Newfoundland and surrounding areas.