Tunnel/Deep Foundation Construction and Rehabilitation Technologies

Written by Xuan Chu, Photos by Xuan Chu and Helen Deng, Edited by Freya Li and Duo Huang.

The Canadian Structural Engineers Association (CSEA) hosted an engaging workshop on Tunnel/Deep Foundation Construction and Rehabilitation Technologies on April 1, 2025, in Oakville. The event gathered a vibrant mix of professionals, all eager to immerse themselves in meaningful learning experiences and forge valuable connections with one another. CSEA was honored to welcome speakers from the ACI Convention to share their insights at this workshop.

Haixue Liao, President of CSEA, delivered welcoming remarks to open the event. He emphasized CSEA’s commitment to fostering professional growth within the engineering community and expressed gratitude to all the speakers, committee members, and volunteers.

Joyce Zhang, Senior Manager from Metrolinx, moderated the technical session.

Gene Latour, VP Sales for Pultrall/V-ROD, introduced the Glass Fiber Reinforced Polymer (GFRP) rebar for concrete structures. Fiber-reinforced polymer (FRP) rebars prevent corrosion when compared to traditional reinforced concrete with black steel rebars. GFRP rebar is ideal for pedestrian bridges, precast bridge components, tunnels, airport runways, water treatment plants, and transit/LRT systems, as well as electrical substations. Using composite reinforcement with FRP is 30% less expensive than traditional design methods and materials, and it can be up to four times lighter than steel rebar. This makes it much easier to handle, which further reduces costs for shipping, handling, and installation. To date, it has been utilized in hundreds of infrastructure projects.

Boris Caro Vargas, General Manager of Dextra in North America, presented FRP anchors and their applications in ground engineering. FRP tendons are post-tensioned from the external face of the ground immediately after installation and are typically designed to help prevent deformation of the ground or soil-retaining structures. This type of anchor is advantageous for soil retention and stabilization.

One common application for active anchors is anchoring retaining walls during excavation work; to prevent wall displacement, the anchor is pre-loaded and made of composite material, which is inherently cuttable. Furthermore, the tendons can be excavated with standard equipment, so anchor removal is never necessary. Other applications include the Soft-Eye Solution in the tunnel and mining sector, designed to ensure efficient and safe excavation. A typical example is the Soft-Eye FRP wall, which allows for easy penetration of Tunnel Boring Machines (TBM) through retaining walls. The design of the Soft-Eye enables precise control of the margin of error. This method serves as the fastest, simplest, and safest way to create tunnel openings. Boris also presented sonic logging tubes that assess the condition of deep foundations.

Haixue Liao, Regional Manager from Vector Corrosion Technologies, presented tunnel rehabilitation strategies. Concrete evaluation and protection are vital components for transit structures and tunnels. He discussed ACI 562 and the ICRI Manual, which serve as the guide and code for assessing, repairing, and rehabilitating existing concrete structures. ACI 562 requires mandatory concrete evaluation and assessment to identify the conditions and root causes of the concrete deterioration and establish the goals of rehabilitation solutions. Research by the Bureau of Reclamation found that Galvashied Anode reduced total corrosion by 80% compared to the control, as well as Sealer & Rebar Coating reduced corrosion approximately by 60% and 40%, respectively.

In the case study of a major tunnel rehabilitation, Haixue introduced the concrete preservation process, which included identifying issues such as cracks and spalling, performing evaluations, developing rehabilitation strategies, and completing repairs. Based on the conditions survey, distributed galvanic anodes for the ceiling and wall refacing were designed and installed, while discrete XP anodes were placed in the service tunnel and vent shafts to ensure long-term protection for the tunnel structures.

Nikolay Tikhovskiy, Business Development Manager at Pullman Services, presented CFRP and its applications in pipe wrapping. Similar to how rebar reinforces concrete, carbon fiber reinforced polymer (CFRP) provides structural support, while the epoxy functions like concrete by bonding the system and transferring loads. The CFRP lining system must be tailored to the specific loading requirements and installation environment. Design considerations include the number of layers, their orientation, such as hoop, longitudinal, or glass, and the method of load transfer at the termination points. Due to the many variables involved, the final system must be customized to meet the unique design criteria of each project.

Bill Horne, Vice President of the NDT Division at VCS Engineering, discussed non-destructive techniques for tunnel evaluation, including Impact Echo (IE) and Pulse Velocity (PV) using sonic NDT systems. He highlighted the use of tomographic imaging, petrography for ASR detection, and chloride content analysis to assess concrete integrity and deterioration in tunnel structures.

CSEA appreciates that numerous volunteers collaborated to help organize this event, including Xuan Chu, Helen Deng, Jenny Wang, Huimin Zhou, and Dean Wilson.

CSEA extends its gratitude to the venue sponsors, Vector Restoration and Pullman, as well as to the coffee sponsor, Pultrall.