TBM Excavation of Long and Deep Tunnels Under Difficult Rock Conditions

The aim of the present report is to:
• Introduce a common technical
language and a simplified classification
on the main geotechnical hazards
that may be encountered during the
excavation of long and deep tunnels
crossing difficult rock conditions;
• Analyse the influence and the
consequences of these phenomenon
regarding the various TBM types;
• Provide recommendations for the
design, for the selection of the TBM
type and for the mitigation measures
to be implemented on-site.
The Appendix of the report is a worldwide
date base collected by the members of
the ITA Working Group 17 on the TBM
tunnelling experience in difficult rock
conditions gained over the last 20 years.
The present report focuses on hazard
scenarios that are associated – or their
magnitude is by far increased – by the
high overburden. However, as for more
shallow tunnels, other hazard scenarios
may be encountered during the tunnel
construction of long and deep tunnels (e.g.
rock falls, swelling, packing of fines around
the shield, karstic phenomena, gripper
bracing problems, environmental aspects
as gas, radioactivity or asbestos etc…),
and so have to be additionally considered
in the design phase of a project.
In the same idea, the following nongeological
related hazards are not handled
in this report: fatigue of the workforce
due to long travel distances, logistic
difficulties in long tunnels, excessive wear
and replacement needs for equipment
and materials due to long construction
times, maintenance needs for the already
constructed parts of the project, and
personnel fluctuation.

  • Published in: 2017
  • Author: WG 17
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