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Combisegments®

Permanently prepared for the future: Tunnel lining with segments and concrete protection for sewage tunnels in one step

The Regional Municipality of Peel is expanding the sewage system in Mississauaga, Ontario, Canada. The various tributaries to sewage collectors as well as various local conditions define the location and depth of the segmentally lined tunnel.

In the inflow and outflow area of a shaft about 30 meters deep, due to strong turbulence there is an increased occurrence of sulfuric acid gases, which accelerate the carbonation of the concrete and thus corrosion of the reinforcement. For this reason, the planners of the approximately 3.8 kilometer long "Mississauga West Trunk" sewage collector specified increased concrete protection with HD-PE liners for this area.

In consultation with the client and the contractor, in compliance with the technical specifications, Combisegments® panels from Herrenknecht Formwork with a 5 millimeter Sure Grip Liner (with signal layers) were used for the first time in North America. After an initial adjustment phase, the Combisegments® panels with a Daetwyler M389 20 HK-CS gasket were put into the mould specially designed by Herrenknecht Formwork and cemented in place.

Tunnelling with the Combisegments® was as efficient as the segment production itself. The use of the existing vacuum erector as well as the closing of the segment openings after ring building were made possible. The use of centering and connecting dowels and a guide bar in the longitudinal joint allowed segment construction without the need for any bolted connections. The quality of the lining was shown in only minimal offsets (<0.5 cm) and the excellent joint pattern optimizes the drainage performance and the necessary permanent protection of the concrete.