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From the Editor's Desk - 06 Aug 2010
The ultimate limiting factor of TBM diameter sizes is often debated. From 10m to 12m, to 14m and now, 15.55m diameter is the largest TBM in production for a tunnel project in Italy. Some say there is no immediate limit for TBM diameters as machines of up to 19m and more are in mechanical design. By contrast, it might be more practical issues, such as transportation of the machine to site, that present the controlling factor. A truck of any greater length, or a load of any greater bulk or weight for example, might have prevented transportation of the TBM drive unit and componants up the narrow village lanes and roads of Switzerland to a hydro scheme project site. Whether by sea, land, or even by air, organising the transportation of TBMs to sites and ensuring safe arrival has to be an expertise all its own.
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