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PRECAST CONCRETE ELEMENTS170 CPI %u2013 Concrete Plant International %u2013 6 | 2025 www.cpi-worldwide.comIn the field of underground works, accuracy is not optional: it is an essential condition for safety, durability and performance. Tunnels, whether railway, road, metro, or for water and energy networks, must meet significant geological and technical constraints. Each segment, a constituent element of the final ring, must be dimensioned and manufactured with extreme rigor. It is within this demanding context that CBE, a specialist in segment moulds and automated precast plants, has built over nearly 40 years a unique expertise in manufacturing tolerances.Expertise forged through International ExperienceSince its creation in 1987, CBE has supported more than 650 projects worldwide. From Asia to the Americas, through Europe, the Middle East and Oceania, segments produced in its moulds can now be found on every continent. This international experience provides a unique database, enabling the design office to capitalize on a wide range of geometric configurations and site constraints.Each tunnel project has its own specificities: ring diameter, geological conditions, expected construction speed, type of concrete used... To address these varied challenges, CBE has developed expertise that systematically integrates the issue of dimensional tolerances from the design phase onward.Stringent standards, adapted to tunnel specificsUnlike other industrial sectors, tunneling does not yet benefit from an international standard regarding dimensional tolerances for segments. Most projects today rely on the recommendations issued by the British Tunnelling Society (BTS), which serve as a shared reference across the industry. For each new project, CBE%u2019s design office bases its approach on these guidelines as well as on its own experience, built over 38 years of practice.Tolerance studies are carried out as early as the preliminary design phase. Depending on the geometry of the segments, the client%u2019s specifications for each dimension of each segment type and the tunnel%u2019s specific constraints, CBE defines extremely fine margins for its mould dimensions: from a tenth of a millimeter up to a millimeter. These calculations consider not only the required accuracy of the segments, but also industrial feasibility and repeatability across several hundred production cycles. They are then transmitted to the mould manufacturing teams, who ensure strict compliance.Concrete moulds accurate to a tenth of a millimeter, essential for tunnel reliabilityCBE Group, 37550 Saint Avertin, France Segment demoulding thanks to an Acimex vacuum lifter Mould CBE and Acimex vacuum lifting device for precast segments