faster than it might in other regions of the country. A compromised structure will exacerbate water infiltration and create risks to the utility services within them, as well as the roads, walkways, and infrastructure above them. In some cases, remediation can involve removing the top and rebuilding in place. In other instances, remediation isn’t as straightforward. Regular tunnel inspections are vital for identifying potential damage and tracking degradation, but underground utility tunnels are often classified as confined spaces and require special safety precautions to ensure the safety of the inspection crew. Beyond the applicable personal protective equipment (PPE), air monitoring, heat monitoring, and emergency egress plans should be carefully considered and strictly followed at all times. During a typical inspection, visual evaluations, along with concrete soundings, are performed to gauge tunnel conditions. Signs of cracked or delaminated concrete, exposed rebar, or water infiltration are documented and tracked during future inspections for signs of worsening conditions. For brick tunnels in particular, inspection is predominantly visual, identifying mortar loss, brick displacement, bowed walls, and open joints. The inspection can also move beyond just the tunnel structure, to include the utility piping within . Water infiltration can quickly damage piping, insulation, and pipe support systems so sump pumps and drainage systems are checked for proper operation. Pipe supports and expansion joints are thoroughly reviewed for heavy corrosion that
may prohibit movement needed to compensate for thermal expansion as operating conditions change within the piping systems. Strategies for Longevity Various maintenance and rehabilitation strategies can be adopted to help sustain and optimize utility tunnels for extended service life. One key consideration is preventing moisture and standing water from infiltrating the tunnels as such conditions can lead to the deterioration of piping systems, pipe supports, and the overall structural integrity of the tunnel. A proactive approach involves designing new tunnels at greater depths, providing separation between the tunnel top and the surface to allow waterproofing systems to be installed not only on the sides, but wrapped around the top as well. Of course, this is impossible for a tunnel that has been in the ground for decades, so other considerations will be needed to address any issues found during routine inspections. Since water can be very damaging to a utility tunnel system, adding provisions for drainage at low points, fixing broken sump pumps, and sealing infiltration points all become crucial steps in ongoing tunnel maintenance. When minor cracks in concrete tunnel structures are found and water has begun to seep in, epoxy injections can be used to stabilize the situation and keep the cracks from worsening. Where minor delamination or spalling is found, repairs can be made per American Concrete Institute (ACI) and International Concrete Restoration Institute (ICRI) standards. Generally, these repairs involve isolating any damaged concrete from sound concrete, removing the damaged sections, and patching
27
Summer 2024 csengineermag.com
Made with FlippingBook Annual report