JUL 2018


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55 Rail Tunnel Seepage Solution CW contributing writer Karen Mason has been researching and writing about the composites industry for more than 25 years. processing. A standard pultrusion bath was unworkable because some components of the ACCIONA mixture would settle to the bath's bottom. Resin injection also was problematic because of the filled resin's very high viscosity. Bansal's team worked with several industry partners on modifi- cations to the resin system, the resin injection system and the injec- tion points that ensured good delivery and wetout of all the glass filaments with the filled Crestapol 1212 resin. Additives provided by BYK-Chemie GmbH (Wesel, Germany) helped ensure uniform wetting and dispersion of inorganic fillers in the resin mixture. LUM Industry (Boisseuil, France) developed and manufactured the pultrusion mold. Final cycle time for the carefully engineered pultrusion process was 34 minutes per panel. Additional benefits e composite lining system covers the 18m arc of the tunnels with a pair of panels. e 9.2m panels overlap by 20 cm at the tunnel apex, which is sufficient to keep water from leaking through the seam — a "path of least resistance" away from the seams is generated by gravity and the water channels that the panels create. Likewise, water won't leak through the long edge seams. Bansal explains, "e lateral overlap along the edges creates a kind of interlocking, and the mechanical forces [from flexing and anchoring the panels] prevent the panels from moving during installation and usage, thereby keeping the interlocking intact." When water travels down through the channels, it empties into concrete canals on either side of the tunnel floor and travels out of the tunnel. Standard transportation equipment can accommodate products up to 10m in length and 1.5m wide, so the paired approach allowed ACCIONA to employ a cost-effective means of transportation to the site. e standard trucking option is also limited to a mass distribution of approximately 8 kg/m 2 , a limit with which the light- weight composite panels easily complied. Further, the composite panels could be installed using standard installation machinery already on site. Each of these factors helped speed installation. Importantly, the panels also are positioned in such a way that the tunnel structure's ring segments can still be inspected as required. Other characteristics of composite materials enhanced the project's cost efficiency and diminished its environmental impact compared to other material systems, Bansal says. "Steel panels would have had to be galvanized," he notes. "Otherwise, corrosion and rust would contaminate the water. A steel structure would also require electrical grounding." In contrast, the composite panels offer easy maintenance and high corrosion-resistance. Production and installation of the composite panels generated significantly lower CO 2 emissions than might otherwise have been produced with alternative approaches. Because of the efficiency with which ACCIONA worked to waterproof the twin tunnels, one of the pair was opened to broad- gauge trains in 2016. e other tunnel opened later that same year. It is hoped that completion of the high-speed rails and the inau- gural high-speed ride to Asturias will take place sometime soon after 2020. Multiple advancements Asked about the innovations generated by this project, Bansal mentioned the application (first-of-its-kind tunnel lining system), the panel and material design, and the process modifications needed to pultrude the panels in a timely manner. He believes, though, that the most innovative aspect of this project was "designing a solution to a real-world problem. We had to prepare the team to make the panels and, in a very limited time, start up production and continue for two years to make consistent, quality panels." His pride in the result is apparent — and well deserved. Formable panels fill the bill The flexibility of the cured material system allowed ACCIONA to conform and install the flat panels to the curvature of the tunnel wall while maintaining structural integrity. Source | ACCIONA

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