Meeting Minutes: Preparation for the comparison of the 100km
options
Date: 02.09.15
Location: CERN
Participants: M. Benedikt, C. Cook, V. Mertens, J. Osborne, P. Lebrun, Y. Robert (CERN)
Y. Loo, C. Sturzaker (ARUP)
J. Brasser, P. Wieser (AMBERG)
J.F. Hotellier, C. Thomas (GADZ)
1. Introduction and Agenda (J. Osborne, C. Cook)
John explains that CERN are currently making a comparison between two options for the positioning
of a 100km FCC tunnel (and accompanying shafts, caverns etc.) within the Geneva Basin. This
comparison will be comprised of two main studies:
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Extension of the study boundary within TOT by Arup
Comparison of the two options from a civil engineering perspective by Amberg
Amberg are also currently conducting a risk assessment for the FCC. All of these studies are likely to
require additional geological information and the agenda for the meeting is to discuss what
information is required and how this should be obtained. The geological advisors, GADZ, are present
to discuss this topic.
Charlie presents the two 100km options. The ‘intersecting’ option intersects the LHC in plan view. A
section of this tunnel travels through the limestone in the Jura. In order to avoid this limestone,
CERN are investigating the ‘non-intersecting’ option which lies outside of the LHC in plan view. The
‘non-intersecting’ option avoids the Jura limestone in the NW but lies outside of the TOT study
boundary in the SE. It is clear that the section of the ‘non-intersecting’ tunnel that lies outside of the
study boundary will be travelling through limestone in the Pre-alpes. However, the current model in
TOT does not show this and an extension to the study boundary is required prior to Amberg’s
comparison of the two options. A report written by GADZ on the geology of the Pre-alpes is
introduced.
2. Extending Study Area within TOT (Y. Loo)
Yung explains that the Pre-alpes region (where an extension of the data in the model is required) is
very complex. It will be important to clearly understand the lack of reliability and level of uncertainty
that a geological model of this area will have. The goal of extending the study boundary should be to
identify feasibility and fatal flaws of the 100km ‘non-intersecting option’. The geology in the model
will be at a sub-regional scale. Uncertainty at rockhead levels, a fuzzy logic, should be clear to the
user of the model. A cross-section of the region is shown and the path of the FCC through this region
is divided into 5 geological sections.
Comments:
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TOT should show no data for regions outside of the extended study boundary (J. Osborne)
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The geology in this region of the Pre-alpes is particularly difficult to map due to its
complexity. Any drawing of this region will merely be an interpretation of what the geology
‘might’ be like (J.F. Hotellier).
Amberg understands that there is a high level of uncertainty inherent in geological
interpretations with very limited available data (J. Brasser)
P. Lebrun asks GADZ about the feasibility of conducting seismic sounding in the region
J.F. Hotellier replies that seismic soundings are very unreliable and difficult to conduct in
mountainous regions.
J. Brasser suggests that any cross-sections of the geology in this region that GADZ can
provide will be useful for their studies
Y. Loo suggests that once the study boundary has been extended, cross-sections from GADZ
should be used in conjunction with outputs from the model.
3. Overview of Amberg studies and geological investigation methods (J.
Brasser)
Johann Peter presents the current understanding of the civil engineering (what we know). The risk
assessment study is then presented. The risk assessment is divided by construction elements
(tunnels, shafts and caverns) and geology. Hazards, mitigation methods and level of risk for each
division are detailed. A proposal for the next steps is presented, this includes; longitudinal profiles
for each zone (as was provided for the Mandallaz), define geotechnical properties of soil/rock of
each zone, verify construction methods for each of the 36 construction elements (12 shafts, 12
tunnel sections and 12 caverns). Longitudinal profiles would provide useful geological information
for both the risk assessment and 100km options comparison study.
Comments:
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The unit weights developed in the previous study may underestimate the risks under
discussion of tunnelling through the Jura limestone (P. Lebrun)
The Amberg metrics helped to begin quantifying the various options studied before
focussing on 100kms, but now a more detailed, section by section, study should be
performed by Amberg to compare the two 100km options and the metrics will not be used
(C. Cook)
4. Geology in the Pre-alpes and geological investigation methods (C. Thomas)
Cyril presents the data currently available in the Pre-alpes region. The best source of data is the
Annecy-Bonneville geological map. Some boreholes have been drilled for geothermal studies but
these are short and the data is unreliable. It is recommended that Arup and GADZ should not
attempt to differentiate between the different types of limestone in the Pre-alpes region. The model
and longitudinal sections should aim to differentiate between limestone and molasse only. Cyril
presents the geological conditions of the FCC section by section. It is noted that the quality of the
molasse is uncertain in the l’Arve valley region, there may be issues with water at depth in the
Mandallaz limestone and also risk of hitting water in the Jura. The geological complexity and
difficulty of tunnelling through the Pre-alpes limestone is again emphasised. Geological investigation
methods are presented. These are seismic lines or boreholes and the execution, applications and
cost of each are described.
Comments:
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Longitudinal sections of this region will be very helpful for Amberg (J. Brasser)
The extension of the study boundary within TOT should begin once longitudinal sections are
received from GADZ (Y. Loo)
A dedicated GIS site on CERN’s computer infrastructure is being created by Youri. This will
help GADZ, Amberg and Arup to view the locations of the FCC traces in more detail. Satellite
imagery of the region and a Digital Elevation Model will be included in the map (Y. Robert).
The timeframe for the preparation of longitudinal cuts by GADZ should be the end of
September (J. Osborne)
Actions (for completion in September 2015)
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Complete dedicated GIS webpage for FCC at CERN – CERN
Prepare longitudinal sections for use by Amberg and Arup – GADZ
Delete data outside of extended study boundary in TOT – ARUP
Prepare TOT in preparation for the extension of study boundary once information from
GADZ is received – ARUP
Await receipt of longitudinal sections from GADZ and extension of the study boundary in
TOT before commencement of the ‘comparison of the 100km options’ study - AMBERG
Long term actions
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Be ready to present initial results of the comparison between the two 100km FCC options by
the end of 2015