Federal Office of Topography swisstopoSwiss Geological Survey

3D Geological Model of the Mont Terri Anticline

Swiss Geoscience Meeting 2008

Roland Baumberger1, Paul Bossart1, Urs Eichenberger2, Andreas Kühni1, Christophe Nussbaum3, Nils Oesterling1, Eric Weber2

1 Swiss Geological Survey, swisstopo, CH-3084 Wabern2 SISKA - Swiss Institute of Speleology and Karst-Research, CH-2301 La Chaux-de-Fonds3 Geotechnical Institute Ltd, CH-2882 St-Ursanne

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• Introduction• The 3D geological model of the Mont Terri anticline • Outlook

Content

Definition of 3D Geology *“3D geology is the interaction of 3D modelling, 3D visualization, data handling and analysis”

* by the Swiss Geological Survey

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Introduction - Background

Why working in the domain of 3D geology?• Geology is 3D • Key technology • Great importance

Supply models for further applications

First step• 3D model of the Mont Terri anticline

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Aims• To develop a 3D model of the Mont Terri anticline• To describe the necessary steps in a “cook-book”• To present the 3D model as movie & VRML-scene• Side-effect

• To check the consistency of 2D profiles

Methodology• Using maps, measurements etc. as input data• Deriving a “simplified model” of the tectonic setting• Iterative refinement of the model

Introduction – The Mont Terri model

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Introduction – The Mont Terri model

Team

Modelling• ISSKA, La-Chaux-de-Fonds• Geotechnisches Institut, St. Ursanne

Project owner & reviewing• swisstopo, Swiss Geological Survey

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Introduction – Tectonic interpretation of the Mont Terri region

Based on the Geologic Atlas of Switzerland 1:25’000; sheet ”St.Ursanne”; Laubscher (1963); modified by C. Nussbaum

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Introduction – 3D simplified block diagrams of the Mont Terri anticline

Position of Mont Terri rock laboratory

Nussbaum & Bossart (2008), in Bossart and Thury, swisstopo report

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Geological data Geologic Atlas of Switzerland 1:25‘000, sheet

„St. Ursanne“ Azimuth & dip measurements Geological cross-sections and reports supplied by

science (Uni Basel), industry and SBB Geological maps along Mont Terri galleries

Other data DEM 25 Aerial photos Construction data of the Mont Terri rock laboratory Layouts of highway and railway tunnels as well as

abandoned limestone quarry of St. Ursanne

3D model – Basic data aquisition

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3D model – Applied methodology

Basic data aquisition

Createstructural

model

1a

Inter-/extrapolation2

Complete final model5

Modifystructural

model

4aCreate

new data

4b

Check geological consistency

yes

nono3

OK?

mo

de

lling

pro

cess

Data preparation

Transfer to modelling software

1b

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Difficulties appeared during model construction due to:

• Data density heterogenous spatial distribution

• Data resolution tunnel cross-sections vs. geological profiles

• Ages of samples e.g. 1873-1875 tunnel cross-sections provided by the SBB

• Diverging conceptual models of the geological structure

publishing ages of basic data

3D model – Challenges

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• 3D model Software: Cinema 4D

• 3D scene VRML-format

• Movie presenting the model .avi-format (see movie at swisstopo booth)

• Project report

3D model – Results

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• 3D geology can help to assure quality standards of 2D data

• Identification of contradictions of 2D cross-sections• Verification of „plain strain hypothesis“

• 3D geology is time consuming• 500-800h modelling work

• 3D geology does not provide one stop results, it is an iterative approach

• Construction of detailed models by passing through several loops

• 3D geology is always interpretation (like conventional geological cross-sections and maps

• Results represent only an approximation to the real settings

3D model – Conclusions

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• Combination of the existing Borehole Information System and 3D model

• Finite element modelling (hydrodynamic, stress field etc.)

Outlook – Mont Terri

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Short-term• Development of a conceptual background for the

setup and application of the 3D geology• Implementation of geological 3D modelling software• Development of 3D models of selected regions

Mid-term• Integration of 3D data into swisstopo Data

Management Systems• Establishing of partnerships and networks• Definition of interfaces to other domains

Long-term• Development of nationwide 3D geological models

Outlook – General

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Thank you for your attention.

3D model available at:http://www.isska.ch/SwissTopo3D/index.html

Contact:roland.baumberger@swisstopo.ch

The end - Questions & answers