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[quote user="MidlandMike"]I suspect that failure of the grout along the tunnel liner may have allowed fluid migration and washout.[/quote] That might be a contributing factor. It would lead to high settling. But I think that could be fixed with grout injections. I don't think that it would lead to the abandonment of the TBM ($20 Mio. per TBM) when filling the tunnel segment with concrete. I think there must have happened something more severe perhaps (speculation) collapse of a tubbing segment. Here is a reworked aerial view showing the location of the head of the TBM (Kopf TBM): <a href="https://abload.de/img/zwischenablage03eksn3.jpg">https://abload.de/img/zwischenablage03eksn3.jpg</a>  (source Drehscheibe Online Forum) There are 56 m (183') left to the end shaft. "Schaden" means damage. The additions are based on the offical DB progress report. On the other side of the rail line is another shaft. That was the original end of the TBM tunneling. Between the two shafts a different method using sprayed concrete within frozen soil was suggestion by the owner. That was changed by the contractor with the agreement of the owner to TBM tunneling to the second shaft. This was a first time. But as the TBM has advanced by far from the damage I doubt this was the reason. With a coverage of just 13' the compression forces in the tubbing segments are not very high. So moments and the connections between the segments get more important. I think we have to wait for the results of the investigation. It is not sure in Germany that it will be published. Regards, Volker
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