Material technology developments in shield tunnelling - annular gap mortar, high-strength concrete and fire-protection concrete / Materialtechnologische Entwicklungen im Schildvortrieb - Ringspaltmörtel, hochfeste Betone und Brandschutzbeton

Mechanical tunnel drive methods are gaining ever more significance on account of their mechanisation and efficiency. Mechanical boring can achieve particularly high advance rates in combination with segment lining systems. In order to investigate the load bearing capacity and robustness of segments, high-strength and ultra high-strength concrete segments were made by HOCHTIEF as part of the European Integrated Project TUNCONSTRUCT (www.tunconstruct.org), investigated through numerical simulation and in the laboratory, and then load tested at STUVA in Cologne. The results included an increase of load-bearing capacity in bending of up to 20 %.
The development of segments made of high-strength concrete does indeed enable higher load bearing capacities, but there are applications under very high overburden and related pressure where this alone is not sufficient. For such cases, a compressible mortar has been developed for the annular gap filling. This has a compression potential of up 50 % and is capable of absorbing deformation of the rock mass and thus reducing the loading of the segment lining. This type of mortar has been successfully used in a large-scale trial in 2009 at the Jenbach Tunnel in the Inn valley, including the manufacture of the mortar on the construction site, the transport chain to the TBM and the injection into the annular gap.