Expert System for the Modelling of Global Risks on Tunnel Projects

Work Package 8

In order to improve cost effectiveness in the field of tunnelling, it is vital to manage the uncertainties linked to ground conditions and construction method.

Cost and programme overruns can sometimes be spectacular, and are often caused by a lack of geological investigation and/or an inappropriate construction method. It is also accepted that attempting to cut costs on initial ground investigation can prove very costly in the end.

On the basis of a concept initiated by Professor Herbert H. Einstein at the Department of Civil and Environmental Engineering – MIT, the Laboratory for Mechanics of Rock (LMR) of the Swiss Federal Institute of Technology in Lausanne (EPFL) has co-developed a methodology and a software package called Decision Aids for Tunnelling (DAT), which allows the risks associated with geology and construction method to be quantified, and the cost and construction time uncertainties to be induced.

The analysis is conducted by simulating in a probabilistic manner and round- or cycle-wise the construction of the whole tunnel network, including shafts, adits, etc.. In that this tool is unique. Up to now EPFL has applied DAT on the following projects: AlpTransit Gotthard and Loetschberg base tunnels, HSL Lyon-Turin, Gibraltar crossing tunnel, and on other preliminary design studies. Present limitations of the software and the absence of commercial approach of its developers (University laboratories) explain its current confidential use.

The objectives of the NeTTUN project are to implement significant improvements to DAT in order to achieve:

• A high reliability by basing the input on the findings of actual tunnel construction,

• A method used both in design stages AND during tunnel construction.