ReferencesBastiaens, W.; Bernier, F. and Li, X.L. (2007). SELFRAC: Experiments and conclusions on fracturing, self-healing and self-sealing processes in clays. Physics and Chemistry of the Earth, 32 (8‒14): 600‒615. Bernier, F. et al. (2007). SELFRAC–Fractures and self healing within the excavation disturbed zone in clays. Final Report. 5th EURATOM Framework Program, Contract No. FIKWCT2001-00182. European Comission, Luxembourg. Bossart, P.; Meier, P.M.; Moeri, A.; Trick, T. and Mayor, J.C. (2002). Geologic and hydraulic characterization of the excavation disturbed zone in the Opalinus Clay at the Mont Terri Rock Laboratory. Engineering Geology (66): 19‒38.Buzzi, O.; Hans, J.; Boulon, M.; Deleruyelle, F. and Besnus, F. (2007). Hydromechanical study of rockmortar interfaces. Physics and Chemistry of the Earth (32): 820‒883. Ferrari, A.; Favero, V. and Laloui, L. (2016). One-dimensional compression and consolidation in shales. International Journal of Rock Mechanics and Mining Science (88): 286‒300.Gutierrez, M.; Oino, L.E. and Nygard, R. (2000). Stress-dependent permeability of de-mineralised fracture in shale. Marine and Petroleum Geology (17): 895‒907.Heath, J.; (2011). Pore networks in continental and marine mudstones: characteristics Dewers, T.; McPherson, B.; Petrusak, R; Chidsey, T.; Rinehart, A. and Mozley P. and controls on sealing behavior. Geosphere, 7(2): 429‒455.

Heitz, D.; Trick, T. and Buhler, C. (2003). Selfrac (SE) Experiment: Long term plate load experiment. Unpublished Mont Terri Technical Note 2003-51.Kaufhold, A.; Halish, M.; Zacher, G. and Kaufhold S. (2016). X-ray computed tomography investigation of structures in Opalinus Clay from large-scale to small scale after mechanical testing. Solid Earth (7): 1‒13.Labouise, V.; Escoffier, S., Gastaldo, L. and Mathier, J-F. (2009). Self-sealing of localised cracks in Boom and Opalinus Clay hollow cylinders. In: Proceedings of the European Commission TIMODAZ-THERESA International Conference, Luxembourg.Shaw, H. (2010). The FORGE (Fate of Repository Gases) pan European project. Clays in natural and engineered barriers for radioactive waste confinement, Fourth International Meeting, Nantes, France. Thöny, R. (2014). Geomechanical analysis of excavation-induced rockmass behavior of faulted Opalinus Clay at the Mont Terri Underground Rock Laboratory (Switzerland). PhD Thesis. Department of Earth Sciences, ETH Zurich. Zhang, C-L. (2011). Experimental evidence for self-sealing of fractures in claystone. Physics and Chemistry of the Earth (36): 1972‒1980.

Drilling Campaigns and Laboratory Testing

Fig. 4. Conceptual layout of drilling and testing in relation to refraction seismic lines shown for a sidewall in gallery 08. A similar concept will be used in gallery 98 to design the testing and choose drilling locations. In total, three drilling campaigns will take place with the first in April 2018. Sites of drilling will be based upon the outcome of the seismic refraction results targeting rock volumes of high/low seismic velocity or, in the case of gallery 08 where previous tests were conduc-ted in 2008, in locations where changes from the initial tests are identified. At each drilling campaign, Opalinus Clay cores will be logged and samples will be taken for laboratory analyses.

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 [m]

side wall

crown

Ph

as

e 2

3P

ha

se

24

Seismic source position in and behind shotcrete

1-component geophone installed in and behind shotcrete,in total 11 lines (4 without shotcrete)

Boreholes (84/42 mm) for sampling, geophysical logging,permeability testing (hydr./pneum.) (Drilling Campaign 2)

Explor./sampl./geophys. logging borehole (84mm) spacedregularly or targeting velocity anomalies (Drilling Campaign 1)

Fluorescence-doped resin injections in pilot borehole andovercoring (array or single hole) (Drilling Campaign 3)

Test site for detailed in situ experiments (Drilling Campaign 2):The selection and layout of test sites will be based on geophysicaldata interpretations and results from first drilling campaign. Ideally,coring, borehole logging, pneumatic/hydraulic testing will be carriedout at the same gallery section.CORING, BOREHOLE LOGGING, PERMEABILITY TESTINGat 5-m-scale (Phase 24)

Example: Gallery 08 (not including existing boreholes)

invert

Detailed in situ experiments (Drilling Campaign 3):RESIN-INJECTION/OVERCORING at 2-m-scale (Phase 24)

Reconnaissance experiments (Drilling Campaign 1):CORING, BOREHOLE LOGGING at 20-m-scale (Phase 23)

Drilling Campaign 1

Drilling Campaign 2

Drilling Campaign 3

Goal: Identify changes in EDZ properties over time at the gallery scale and identify sealed / unsealed zones for further tests.Collect core material for laboratory testing.

Laboratory tests: Mineralogy (XRD), geo-chemistry (scanning-XRF), porosity (Hg intrusion), volumetric water content and water uptake (Enslin-Neff)

Goal: Detailed characterization of two sites at the 5-m-scale. Obtain EDZ per-meability properties. Collect core material for laboratory testing.

Laboratory tests: Mechanical tests (e.g., EDZ fracture surface stiffness via indentati-on), mineralogy (XRD), geochemistry (powder-XRF, exchangeable cations, CEC)

Goal: Characterization of the EDZ fracture network and its connectivity in sealed / unsealed EDZs at the 2-m-scale.

Laboratory tests: Micro- and nanoscale structural analyses (2.5D and/or 3D) of EDZ fracture surfaces and of non-damaged reference samples using SEM / FIB-SEM

Seismic Refraction Study at Gallery Walls

Fig. 2. (Above) Layout of seismic refraction lines for the SE-P experiment.

Fig. 3. (Right) Geophones were placed into Opalinus Clay through drilling of short bore-holes through the shotcrete. Striking a metal rod anchored into the Opalinus Clay was used as the source (A). All lines were first tested with the placement of sources and receivers in shotcrete (B).

A B

Source Geophone2 m

Invert

Crown

These lines were first tested in 2008 (Thöny, 2014) and repeated.

Main Fault

Gallery 08

Gallery 98

Crown

Two lines per gallery tested with shots and receivers installed in the Opalinus Clay formation (Fig. 3A)

2 m

55

2 m

60

64

67 69

Cross Section

Cross Section

N

Invert

Crown

Crown

All lines were first tested with geophones installed in shotcrete and source (hammer) against the shotcrete surface (Fig. 3B).

60 55

Fig. 1. Location of experiment sites (galleries 08 and 98) for the SE-P experiments (figure modified after Kaufhold et al. 2016).

Location

BackgroundSelf-sealing refers to the reduction of permeability of natural or induced fractures in a rock mass through mechanical/hydromechanical, hydrochemical, and/or biological processes. These processes can include compaction and consolidation, creep, swelling, slaking, formation of mineral precipitants along fracture sur-faces, among others. Since sealing can reduce the hydraulic conductivity of damaged rock masses, an under-standing of the mechanisms driving self-sealing is essential in understanding long-term repository safety.

Self-sealing has been inferred from or observed by in-situ experiments at Mont Terri such as the SELFRAC, EH (self-healing), and HG-A (hydrogen gas) experiments (e.g., Bossart 2002; Heitz and Buhler 2003; Bernier et al. 2004; Shaw 2010). Sealing processes have also been observed in laboratory tests (e.g., Gutierrez et al. 2000; Bernier et al., 2007; Buzzi et al. 2007; Labiouse et al. 2009; Zhang 2011; Ferrari et al. 2016). However, the in-situ processes in EDZs have still not been studied in sufficient detail spatially and temporarily. Our study focuses on identifying self-sealing processes in-situ and linking laboratory results with in-situ measurements and observations at larger (5–20 m) scales to those made at micro- and nanoscales.

Scientific Questions¦ How do EDZs evolve over 10–20 years ?

¦ ¦ How do variations in rock mass properties

and EDZ characteristics effect self-sealing ?¦

¦ What are the processes and mechanisms most important in sealing of EDZs ?

Research Approach

¦ Investigation of sealing processes acting in previously studied, old (10–20 years) EDZs

with well-understood initial extents

¦ Characterization of changes in EDZ properties at the tunnel scale (5–20 m) through seismic

refraction tomography, borehole logging (IVM, ERT, OPTV), pneumatic/hydraulic testing, and

resin-injected boreholes and overcores

¦ Identification of sealing processes through laboratory tests on core samples (mineralogi-cal, geochemical, petrophysical, macro- and microscale structure, mechanical properties)

SE-P Project: Self-Sealing Processes in Old ExcavationDamaged Zones at the Mont Terri URL

1Department of Earth Sciences, ETH Zurich; molly.williams@erdw.ethz.ch

1* 1 1Molly Williams , Martin Ziegler , Simon Löw