The world’s claimed largest TBM is making good progress on Holland’s 8km long Groene Hart high speed rail tunnel. Contractor, the Bouyges/Koop JV, started up the giant 14.9m diameter NFM at the end of last year and have made 360m so far. The JV will drive the 7.2km of single bore tunnel for the next two years through the soft Dutch sandy ground conditions.
The JV chose to construct the tunnel as a US$349M single bore, twin track structure for various financial and environmental reasons. The single tube will create considerably less spoil than the twin 9.3m diameter tunnels envisaged in the original design and will help keep settlement down to the enforced 20mm along the alignment.
Another bonus is the elimation of expensive cross passage construction. The tunnel tracks will be seperated by reinforced concrete slabs equiped with frequent escape doors. Three escape shafts will be positioned every 2km to exit the tunnel in the event of a fire.
Lining the structure will require the TBM to erect rings of10 x 15t concrete segments and a key designed by Bouygues. Segment are being made in Belgium as Holland lacks the resources for such a segment demand.
The TBM will be monitored using Bouygues’ own PIXIS system that takes a total of 2000 parameter recordings allowing complete control over machine positioning.
This 8km section of the Amsterdam-Rotterdam high speed rail line, being built for the Dutch Ministry of Transport, was forced underground for environmental reasons as it passes through an area of conservational interest.
