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Dear clients,

After an eventful 2016, 2017 promises to be filled with news and events. In the first quarter of 2017, Itasca France organizes three major events in France: a FLAC3D and a Griddle training courses, as well as a one-day workshop in collaboration with Ecole des Ponts ParisTech in Paris. Also, the European Itasca offices will be present at a number of conferences all over the world. We invite you to read carefully the Training/Seminars and Conferences sections and visit us at one of these events!

A sincere thank you for your continued trust and loyalty. Have a restful holiday season - we hope to see you soon in 2017.

The European Itasca team

Consulting

Prediction of tunnel wall damage for the Wittelsheim waste storage

Following the decision to stop storage operations in the Wittelsheim ultimate waste storage, a mixed strategy was developed for its final closure, including first a partial destocking of the waste, and second the confinement of the remaining waste by very low permeability plug, reducing brine inflow and subsequent potential contaminated outflows.
Since the start of the partial destocking operations, it has become clear that tunnel walls are significantly damaged, resulting in a significant reduction of the tunnel sections and in the detachment of rock slabs from the roof. In this context, the prediction of the stress state in the salt around the storage is of great import. Indeed, it can provide an indication on the location of the most damaged tunnels, and help to anticipate difficulties in future destocking operations.
For this purpose, a numerical 3D model was developed with the FLAC3D software. It encompasses all the storage tunnels, as well as the overlaying mining excavations, dating from the 1920s and 70s. It is expected that these excavations, 25m above the storage, strongly influence the stress state around the storage.

Destocking activities to date have highlighted a strong correlation between highly degraded areas, where operations are very delicate, and a local increase in vertical stress as obtained from the numerical model, enabling to better define the future destocking operations and to refine the cost comparison for the different storage & closure solutions.


Mining excavations overlying the storage


Storage excavation geometry


Vertical stress contour before the excavation of the storage, below the mining excavations

 

 

Connectivity, permeability, and channeling in randomly distributed and kinematically defined discrete fracture network models

A major use of DFN models for industrial applications is to evaluate permeability and flow structure in hardrock aquifers from geological observations of fracture networks. The relationship between the statistical fracture density distributions and permeability has been extensively studied, but there has been little interest in the spatial structure of DFN models, which is generally assumed to be spatially random (i.e., Poisson). We compare the predictions of Poisson DFNs to new DFN models where fractures result from a growth process defined by simplified kinematic rules for nucleation, growth, and fracture arrest. This so-called ‘‘kinematic fracture model’’ is characterized by a large proportion of T intersections, and a smaller number of intersections per fracture.

Three-dimensional picture of flow in the sequential kinematic DFN model colored by total flow per fracture

Several kinematic models were tested and compared with Poisson DFN models with the same density, length, and orientation distributions. Connectivity, permeability, and flow distribution were calculated for 3-D networks with a self-similar power law fracture length distribution. For the same statistical properties in orientation and density, the permeability is systematically and significantly smaller by a factor of 1.5–10 for kinematic than for Poisson models. In both cases, the permeability is well described by a linear relationship with the areal density p32, but the threshold for kinematic models is 50% larger than for Poisson models. Flow channeling is also enhanced in kinematic DFN models. This analysis demonstrates the importance of choosing an appropriate DFN structure for predicting flow properties from fracture network parameters.

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arrow Training & Seminars

Itasca will host introductory training courses in Europe:

Code
Location
Dates
Contact
Griddle v1.0 Training course Ecully, France January 16-18, 2017 Itasca France
FLAC3D Training course Ecully, France January 24-26, 2017 Itasca France
Itasca Info Days dedicated to FLAC3D 6.0 Germany Quarter 1, 2017 Itasca Germany
Workshop Itasca/ENPC ENPC, Paris March 7, 2017 Itasca France
FLAC3D/Griddle Training course Gelsenkirchen and Freiberg, Germany March/April, 2017 Itasca Germany

Please visit www.itascacg.com/training for full details.

For users who envisage the need for substantial amounts of assistance, consulting support or customized training course are available.
Accordingly, users are encouraged to submit sample problems prior to the training session for our review and preparation. These problems would then be used as practical applications of the code during the training sessions.

arrow Conferences

Itasca and/or representatives will be attending the following conferences:

Swedish Rock Mechanics Day ("Bergmekanikdagen") March 13, 2017 Stockholm, Sweden
Swedish Foundation Day ("Grundläggningsdagen") March 16, 2017 Stockholm, Sweden
Deep and High Stress Mining March 28-30, 2017 Perth, Australia
World Tunnel Congress June 9-15, 2017 Bergen, Norway
BCRRA 2017 June 28-30, 2017 Athens, Greece
Powders & Grains 2017 July 3-7, 2017 Montpellier, France
Congress International AFTES Paris 2017 "The value is underground" November 13-16, 2017 Paris, France

Slope Stability 2018
Jonny Sjöberg appointed Keynote Speaker :

April 11-13, 2018 Seville, Spain

arrow Recent Publications

Maillot, J., P. Davy, R. Le Goc, C. Darcel, and J.R. de Dreuzy -– (2016), Connectivity, permeability, and channeling in randomly distributed and kinematically defined discrete fracture network models, Water Resour. Res., 52.

Mäkitaavola, K., B-M Stöckel, J. Sjöberg, S. Hobbs, J. Ekman, M. Henschel and A. Wickramanyake – (2016) "Application of InSAR for Monitoring Deformations at the Kiirunavaara Mine". In: Proceedings ISMS 2016, 3rd International Symposium on Mine Safety, Science and Engineering (Montreal, Canada, Aug 15–17, 2016), Paper No. 250.

Perman, F., T. Wettainen, C. Gonzalo and J. Sjöberg – (2016) "Three-dimensional modeling and stress calibration for a complex mining geometry". In: Proceedings RS2016, 7th International Symposium on In-Situ Rock Stress (Tampere, Finland, May 10-12, 2016), pp. 127–138. ISBN 978-951-758-606-1.

Lope Álvarez, D., J. Sjöberg, M. Eriksson, R. Bertilsson, D. Mas Ivars – (2016) "Tunnelling and reinforcement in heterogeneous ground – A case study". In: Proceedings Eight International Symposium on Ground Support in Mining and Underground Construction (Luleå, Sweden, September 12-14, 2016), Paper No. 193.

Vatcher, J., S. D. McKinnon and J. Sjöberg (2016) – "Developing 3-D mine-scale geomechanical models in complex geological environments, as applied to the Kiirunavaara Mine", in Engineering Geology, Vol 203, pp. 140–150 (http://dx.doi.org/10.1016/j.enggeo.2015.07.020)

J. J. Oetomo, E. Vincens, F. Dedecker, J-C. Morel (2016) - "Modeling the 2D behavior of drystone retaining walls by a fully discrete element method", in Int. Journal for Numerical and Analytical Methods in Geomechanics, to publish

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Itasca Consultants S.A.S
64 Chemin des mouilles
FR-69134 Ecully Cedex
France

© 2016 Itasca Consultants S.A.S.