TechSpan® technology

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TechSpan® is a buried precast concrete arch. It generally consists of half arch units that meet at the crown, supported by a footing sized for site specific conditions. The backfill around the arch contributes to the resistance of the entire structure, constraining lateral deflections of the arch under vertical loads (soil-structure interaction).

KIAMA Railway Tunnel techspan terre-armee


The span ranges from about 6m to more than 22m. Height ranges from about 30% to 70% of the span.

Its funicular curve minimizes the tensile forces in the arch, thus creating an axially compressed structure, leading to increased durability and costs savings.

TechSpan® technology results from decades of research and development. The system is designed to accommodate high fills, heavy live loads and altering loading conditions often associated with mining, industrial and railway applications.

With the support of sophisticated Finite Element Method (FEM) analysis, the loads on TechSpan® arches are verified for each step of construction including backfilling sequence.

The components defining a TechSpan® arch are the following:

    • Arch footings (cast-in-place or precast)
    • TechSpan® precast arch (male and female arch elements or single piece depending on the transportation limitations)
    • Cast-in-situ crown beam (for longitudinal connection in the most cases, for stitching the crown in special cases where a 2 pin arch is required)
    • Waterproofing whenever required or geotextile joint protection
    • The backfill (Zone 1, Zone 2 and Zone 3), placed and compacted in layers on both sides of the arch, complying with the Terre Armée Group specifications.

 Installation of TechSpan® arches - Transmission Gully Project in New Zealand

The new TechSpan® catalogue contains most of the common shapes suitable for roadways, railways and hydraulic applications.