Full-face tunnel boring machine

Between May and November 1983, the Grimsel Test Site was excavated using a full-face tunnel boring machine with a diameter of 3.5 metres (total tunnel length approx. 1.1 km; broken-out volume 14,800 cubic metres).

Caverns were also excavated by blasting. Extensions to the tunnel system were made in 1995, 1997 and 2000.

The conditions for tests performed at the Grimsel Test Site are particularly favourable because it contains areas of relatively undisturbed homogeneous rock as well as heavily fractured areas with water-bearing zones (shear zones, fractures, lamprophyre and aplitic dykes).

The division of the GTS into individual test caverns and drifts was made on the basis of the prevailing rock features at these locations and ensures optimum conditions for the performance of specific experiments.

Operating phases

In 40 years of operation at the Test Site, a wide range of investigations have been carried out in many fields, including geology, geophysics, hydrogeology, rock mechanics and nuclide transport. The scientific work performed has been already shown to over 50,000 visitors and has been presented in many papers presented at conferences or published in scientific journals and the extensive list of technical reports given in the publications section.

Phases I and II (1983 - 1990)

In Phases I and II, a comprehensive investigation programme was carried out which included 16 major experiments . In addition to providing detailed information on the geological-hydrological situation, which is required for planning, performing and interpreting later tests, Phases I and II improved the understanding of the interaction between modelling exercises, laboratory experiments and in-situ studies. Progress was also made in developing the methodology for performing scientific investigation programmes under field conditions. Some of the research projects, for example the development of geophysical techniques (underground radar and seismics), the mechanical test of the excavation damaged zone, the heater test and rock stress measurements, were successfully completed during Phase II, others continued during Phase III.

Phase III (1990 - 1993)

Drawing on the experience gained in Phases I and II, the concept developed for Phase III focused on investigating hydraulic and geochemical/physical transport processes in the rock. The experiments during this phase included the fracture system flow test, the ventilation test and the migration experiment. In this phase, the role of associated modelling studies became increasingly important.

Models initially used to interpret field observations were used to predict the results of later experiments and such predictions compared with measured output. This aspect of model testing is particularly important as, in many cases, the manner in which the simulation is carried out can be very objective and, if the "answer" is known, can be biased either consciously or subconsciously. The difference between blind testing of model predictions and testing if a model can simulate particular observations is fundamental, although not evident in the literature.

Phase IV (1994 - 1996)

More than in the previous project phases, specific safety analysis questions guided set up of the investigation programme for Phase IV. The criteria used as a basis for determining the Phase IV programme included the applicability of the results to potential repository sites, an assessment of the chances of success, the suitability of Grimsel as a research site and possible overlap with other national research programmes. Choice of experiments to be included and details of individual research projects were established with input from a range of other national partners. The resultant programme includes testing technology for borehole sealing, further development of seismic tomography, development of methods for characterising the area close to the tunnel and in situ experiments designed to provide a better understanding of transport mechanisms of radionuclides through the geosphere. This experiment culminated in the excavation of the test area and analyses of the distribution of the radionuclides along the test area.

Phase V (1996-2004)

More DETAILS in the Archive of previous GTS projects (1997 to 2004) section of this site.

Grimsel Phase V ran from 1997 to 2004. The focus was on investigating geological barrier effectiveness, demonstration of disposal concepts and site characterisation investigations. All the projects were also designed to contribute to the further development of and assessment of modelling capabilities.

Phase V saw the construction of new caverns at the GTS and experience gained in the use of radionuclide tracers was built on during the investigations of the geological barrier.

GTS phase V can be grouped into three main areas of interest.

• The Engineered Barrier System: FEBEX, GMT and FOM
• Processes in the Geological Barrier: HPF, CRR and GAM
• Site Characterisation and Modelling: EFP and CTN projects

Phase VI (2003 » )

More DETAILS in the Overview of ongoing GTS projects section of this site.
Grimsel Phase VI began on the 1st January 2003 and represents a major step forward in the research carried out at the GTS. The focus of the new research will be the examination of waste disposal concepts on more repository-relevant timescales and conditions and focuses on:

• Development and optimisation of the technology, transporting, emplacing, quality-assuring, monitoring and, if required, retrieving of radioactive waste.
  
  
• Extending past studies of processes in the geosphere (mainly associated with radionuclide mobility) to more closely represent the physical scales (at least 10s of metres) and boundary conditions (e.g. low water velocities) relevant to repository environments. This requires multi-decade duration tests, more than an order of magnitude longer than has been the case in any rock laboratory anywhere in the world to date.
  
  
• Monitoring and extending the knowledge and experience available from the present generation of radioactive waste experts by training the next generation who will actually build repositories

Main experiments at the Test Site

Phase I and II (1983-1990)

 - Exploratory boreholes and geological mapping

AU Excavation effects
BK Fracture flow test (BGR)
EM Electromagnetic high frequency measurements (BGR)
FRI Fracture zone investigation (Nagra/USDoE)
GS Rock stress measurements (BGR)
HPA Hydraulic potential (Nagra)
MI Migration experiment (Nagra/JNC)
MOD Hydrodynamic modelling (Nagra)
NFH Near-field hydraulics (Nagra)
NM Tiltmeters (GSF)
SVP Prediction ahead of the tunnel face (Nagra)
US Underground seismic test (Nagra)
UR Underground radar (Nagra)
VE Ventilation test (GSF)
WT Heater test (GSF)

Phase III (1990-1993)

BK Fracture flow test (BGR/Nagra)
MI Migration test (JNC/Nagra)
MOD Hydrodynamic modelling (Nagra)
ZU Unsaturated zone (Nagra)
VE Ventilation test (GSF/Nagra)
- Large diameter borehole (Andra)

Phase IV (1994-1996)

BOS Borehole sealing (Nagra)
EDZ Excavation disturbed zone (Nagra)
EP Excavation of the MI shear zone (JNC/Nagra)
TOM Further development of seismic tomography (Nagra)
TPF Two phase flow (Nagra)
CP Connected porosities (Nagra/JNC)
ZPK Two phase flow in fracture network of the tunnel near-field (BGR)
ZPM Two phase flow in the matrix of crystalline rocks (GSF)

Phase V (1996-2004)

CRR Colloid and Radionuclide Retardation Experiment (Andra, Enresa, FZK, JNC, Sandia, Nagra)
EFP Effective Field Parameters (BGR)
FEBEX Full-scale High Level Waste Engineered Barriers Experiment (Project lead by Enresa)
FOM Fiber Optic Monitoring (DBE EEIG Nagra)
GAM Gas migration in shear zones (Andra Enresa CSIC UPC Sandia ETH)
GMT Gas Migration in EBS and Geosphere (RWMC Nagra/Obayashi)
HPF Hyperalkaline Plume in Fractured Rocks (Andra Enresa SKB JNC Sandia)

Phase VI (2003 »)

CFM Colloid Formation & Migration
C-FRS CRIEPI’s Fractured Rock Studies
CIM Carbon-14 and Iodine-129 Migration in Cement
ESDRED Test and Evaluation of Monitoring Systems
FEBEXe Full-scale Engineered Barriers Experiment
FEBEX-DP Febex Dismantling Project
FORGE Laboratory Column Experiments
GAST Gas-Permeable Seal Test
HotBENT High Temperature Effects on Bentonite Buffers
ISC In-situ Stimulation & Circulation Experiment
LASMO Large Scale Monitoring
LCS Long-Term Cement Studies
LTD Long Term Diffusion
MACOTE The Material Corrosion Test
NF-PRO Near Field Processes
PSG Pore Space Geometry