OasisLMS

Abstract: With the growing prevalence of tunneling projects in urban centers worldwide, safeguarding existing buried infrastructure, particularly bridge piles and deep foundations, has become a critical engineering challenge. Accurate knowledge of pile length and foundation details is essential to ensure sufficient clearance from proposed tunnel alignments and to mitigate risks to structural stability during construction. However, many older structures lack reliable design or as-built documentation, leaving foundation lengths and conditions uncertain. This uncertainty poses significant risks to the integrity of these foundations, especially when they intersect with new tunneling activities.

This paper addresses the challenges of evaluating unknown pile lengths in the context of protecting existing buried infrastructure during urban tunneling projects. It presents four case studies where foundation investigations were required due to inadequate as-built information. To determine pile lengths and ensure safe clearances, four Non-Destructive Testing (NDT) techniques were employed: Parallel Seismic (PS), Crosshole Sonic Method (CSM), advanced surface Guided Waves, and Length Inductive Testing. These techniques were selected and adapted based on specific site conditions, including access constraints, soil profiles, and surrounding structural configurations.

Each case study highlights the methodologies used to assess pile lengths, the considerations for adapting NDT techniques to site-specific challenges, and the practical implications for maintaining the stability of existing foundations during tunneling. The paper evaluates the advantages and limitations of each NDT method, emphasizing their role in mitigating risks to buried infrastructure and facilitating safer integration of modern tunneling projects with legacy systems. This work provides valuable insights into the importance of tailored investigative approaches in urban environments, where preserving the integrity of critical infrastructure is paramount.

Dr. Hamed Layssi; Dr. FARID MORADI

Annual Conference Proceedings