Assessing Unknown Foundation Lengths: Case Studies of Multi-NDT Applications in Urban Canada

ABSTRACT: With increasing urban development across Canada, accurately determining the lengths of piles and deep foundations has become critical. Piles are essential in civil infrastructure, transferring structural loads to stable soil or bedrock. However, many older structures lack reliable design or as-built records, making it difficult to assess their foundations for reuse or integration with new construction. These uncertainties pose potential risks to structural stability and safety, especially in dense urban areas. Reliable pile length evaluation helps mitigate such risks and supports the sustainable reuse of existing foundations. This paper presents two case studies from Edmonton and Toronto, where various Non-Destructive Testing and Evaluation (NDT-E) methods were used to estimate unknown pile lengths under different site conditions. Techniques such as Parallel Seismic (PS), Length Inductive Test (LIT), and Guided Waves were applied and compared. The results highlight the benefits and limitations of each method, emphasizing the value of a combined NDT approach in supporting safer and more efficient urban development across Canada.