Preprints
https://doi.org/10.5194/se-2021-109
https://doi.org/10.5194/se-2021-109

  03 Sep 2021

03 Sep 2021

Review status: this preprint is currently under review for the journal SE.

Multi-disciplinary characterizations of the Bedretto Lab – a unique underground geoscience research facility

Xiaodong Ma1, Marian Hertrich1, Florian Amann2, Kai Bröker1, Nima Gholizadeh Doonechaly1, Valentin Gischig3, Rebecca Hochreutener1, Philipp Kästli1, Hannes Krietsch2, Michèle Marti1, Barbara Nägeli1, Morteza Nejati1, Anne Obermann1, Katrin Plenkers1, Antonio P. Rinaldi1, Alexis Shakas1, Linus Villiger1, Quinn Wenning1, Alba Zappone1, Falko Bethmann4, Raymi Castilla4, Francisco Seberto4, Peter Meier4, Thomas Driesner1, Simon Löw1, Hansruedi Maurer1, Martin O. Saar1, Stefan Wiemer1, and Domenico Giardini1 Xiaodong Ma et al.
  • 1Department of Earth Sciences, ETH Zürich, Zürich, 8092, Switzerland
  • 2Engineering Geology and Hydrogeology, RWTH Aachen, Aachen, 52062, Germany
  • 3CSD Ingenieure AG, Liebefeld, 3097, Switzerland
  • 4Geo-Energie Suisse AG, Zürich, 8004, Switzerland

Abstract. The increased interest in subsurface development (e.g., unconventional hydrocarbon, deep geothermal, waste disposal) and the associated (triggered or induced) seismicity calls for a better understanding of the hydro-seismo-mechanical coupling in fractured rock masses. Being able to bridge the knowledge gap between laboratory and reservoir scales, controllable meso-scale in situ experiments are deemed indispensable. In an effort to access and instrument rock masses of hectometer size, the Bedretto Underground Laboratory for Geosciences and Geoenergies (‘Bedretto Lab’) was established in 2018 in the existing Bedretto Tunnel (Ticino, Switzerland), with an average overburden of 1000 m. In this paper, we introduce the Bedretto Lab, its general setting and current status. Combined geological, geomechanical and geophysical methods were employed in a hectometer-scale rock mass explored by several boreholes to characterize the in situ conditions and internal structures of the rock volume. The rock volume features three distinct units, with the middle fault zone sandwiched by two relatively intact units. The middle fault zone unit appears to be a representative feature of the site, as similar structures repeat every several hundreds of meters along the tunnel. The lithological variations across the characterization boreholes manifest the complexity and heterogeneity of the rock volume, and are accompanied by compartmentalized hydrostructures and significant stress rotations. With this complexity, the characterized rock volume is considered characteristic of the heterogeneity that is typically encountered in subsurface exploration and development. The Bedretto Lab can adequately serve as a test-bed that allows for in-depth study of the hydro-seismo-mechanical response of fractured crystalline rock masses.

Xiaodong Ma et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on se-2021-109', Anonymous Referee #1, 11 Oct 2021
    • AC1: 'Reply on RC1', Xiaodong Ma, 15 Oct 2021
  • RC2: 'Comment on se-2021-109', Pär Grahm, 12 Nov 2021
  • RC3: 'Comment on se-2021-109', Pär Grahm, 12 Nov 2021

Xiaodong Ma et al.

Xiaodong Ma et al.

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Short summary
Questions such as anthropogenic earthquakes and deep geothermal energy developments require a better understanding of the fractured rock. Experiments conducted at reduced scales but with closer, controlled observation can shed some light. To this end, the Bedretto Underground Laboratory for Geosciences and Geoenergies was recently established in a tunnel in Ticino, Switzerland, with preliminary efforts to characterize realistic rock mass behavior at the hectometer scale.