Profiles

Andrew Frampton

Universitetslektor

Visa sidan på svenska
Works at Department of Physical Geography
Telephone 08-674 75 92
Email andrew.frampton@natgeo.su.se
Visiting address Svante Arrhenius väg 8
Room T 310
Postal address Inst för naturgeografi 106 91 Stockholm

Teaching

Courses at masters level
GE7078 Advanced hydrogeology 7.5 ECTS
GE7051 Permafrost - interactions with ecosystems and hydrology 15 ECTS

Courses at undergraduate level (in Swedish)
GE4029 Kvartärgeologi och hydrologi 10 hp
GE5029 Hydrologi och vattenresurser 7,5 hp
 

Research

Arctic and subarctic hydrology, hydrogeology and transport

Arctic and subarctic environments are particularly sensitive and susceptible to climate change effects, where changes in groundwater systems may strongly impact downstream recipients, affecting water resources and quality. Quantifying degrading permafrost and associated carbon releases also plays a major role in understanding key climate feedback mechanisms.

Understanding the links between permafrost change and its influence on water flow and waterborne carbon transport is important for addressing and quantifying arctic terrestrial feedbacks to climate change. This since many permafrost regions contain large quantities of stored carbon in soil, located near the ground surface most susceptible to effects of warming. As the active layer degrades and deepens, increased gaseous release of carbon-dioxide and methane to the atmosphere is expected, which may potentially be an important positive feedback to climatic warming. The release of stored carbon is however affected by transport of subsurface water to surface water and ecosystems prior to release as gaseous CO2.

This research theme involves investigating climate-driven changes and feedback mechanisms related to the interactions of subsurface hydrogeological flow and transport, permafrost change and carbon releases to the atmosphere and water systems in cold regions, with specific application to northern arctic and subarctic sites along a climate gradient.  The specific objectives include to investigate and quantify process and system links of changing permafrost – hydrology-hydrogeology – waterborne carbon transport – gaseous carbon releases, by developing methodologies for assembling such process and system modelling capabilities. Available observations on relevant change mechanisms are used for model testing and model interpretation of data from several arctic and subarctic sites of on-going field investigations, including, but not limited to, sites located in northern Sweden, Greenland, and Svalbard.

 

Flow and transport in fractured rock

Analysing flow and transport phenomena in sparsely fractured media is important for understanding how natural geological environments function as barriers against transport of contaminants and other substances stored in subsurface geological repositories. Sparsely fractured crystalline bedrock is a favourable environment due to weak advective flow and strong retention properties, where the interplay between advective and dispersive flow strongly impacts both inert and reactive transport. The natural bedrock can thereby delay transport of waterborne substances for considerable amounts of time, allowing sorption and decay processes to limit release to the biosphere.

There are however many challenges involved in characterising, quantifying and modelling subsurface flow and transport, mainly due to great geological complexity and variability of the subsurface. Also, there are limitations in availability of field data and uncertainties related to conditioning models against relevant field measurements, in particular related to flow information, and in being able to describe how meaningful uncertainties impact application-significant assessments.

This research theme involves developing and applying methods for numerical fracture network modelling combined with analytical, semi-analytical and algorithmic approaches to investigate flow, flow pathways, and transport processes in geological fractured media, based on application of relevant field data. In particular, applications towards storage of spent nuclear fuel related to the Swedish and Finnish site characterisation campaigns are considered. Here transport of radionuclide particles is of main interest. Also, applications involving carbon capture and storage (CCS) are considered, where caprocks can act as practically impermeable layers to gaseous carbon release from subsurface storage of supercritical carbon dioxide.

 

Multiphase flow in coupled fractured-porous media

A candidate environment for deep geological storage of spent nuclear fuel is sparsely fractured crystalline rock, since these typically offer low-permeable and long-term stable conditions. However, canister deposition holes and the repository tunnel system need to be back-filled with buffer material, typically containing bentonite clays. Thereby, upon closure, the repository will undergo a multiphase flow process as groundwater seepage re-saturates the subsurface tunnel system.

The prevalence of those transient unsaturated conditions in porous and fractured media generally has a considerable influence on the flow field and thereby also on transport. Specifically, the occurrence of mixed gas-water flows may influence the environment near the deposition holes as well as the physical and biogeochemical processes along potential transport pathways from repository depth. There are numerous scientific investigations of two-phase flow behaviour in soil systems, but much fewer observations for these types of engineered bentonite-clay buffer systems. In particular, effects of buoyancy and bubble trapping may differ in fractured bedrock from those in classical soil environments. A comprehensive understanding of multiphase flows in a coupled bedrock-bentonite system is therefore necessary.

 

Publications

Peer-reviewed articles

Grenier, C., Anbergen, H., Bense, V., Chanzy, Q., Coon, E., Collier, N., Costard, F., Ferry, M., Frampton, A., Frederick, J., Gonçalvès, J., Holmén, J., Jost, A., Kokh, S., Kurylyk, B., McKenzie, J., Molson, J., Mouche, E., Orgogozo, L., Pannetier, R., Rivière, A., Roux, N., Rühaak, W., Scheidegger, J., Selroos, J.-O., Therrien, R., Vidstrand, P., Voss, C., 2018. Groundwater flow and heat transport for systems undergoing freeze-thaw: Intercomparison of numerical simulators for 2D test cases. Advances in Water Resources 114, 196–218. https://doi.org/10.1016/j.advwatres.2018.02.001

Schuh, C., Frampton, A., Christiansen, H.H., 2017. Soil moisture redistribution and its effect on inter-annual active layer temperature and thickness variations in a dry loess terrace in Adventdalen, Svalbard. TC 11, 635–651. https://doi.org/10.5194/tc-11-635-2017

Ströberg, A., Ebert, K., Jarsjö, J., Frampton, A., 2017. Contaminated area instability along Ångermanälven River, northern Sweden. Environmental Monitoring and Assessment 189. https://doi.org/10.1007/s10661-017-5839-0

Dessirier, B., Åkesson, M., Lanyon, B., Frampton, A., Jarsjö, J., 2016. Reconstruction of the water content at an interface between compacted bentonite blocks and fractured crystalline bedrock. Applied Clay Science. doi:10.1016/j.clay.2016.10.002

Gisnås, K., Etzelmüller, B., Lussana, C., Hjort, J., Sannel, A.B.K., Isaksen, K., Westermann, S., Kuhry, P., Christiansen, H.H., Frampton, A., Åkerman, J., 2016. Permafrost Map for Norway, Sweden and Finland: Permafrost map for Norway, Sweden and Finland. Permafrost and Periglacial Processes. doi:10.1002/ppp.1922.

Dessirier, B., Frampton, A., Fransson, Å., Jarsjö, J., 2016. Modeling early in situ wetting of a compacted bentonite buffer installed in low permeable crystalline bedrock. Water Resources Research 52, 6207–6221. doi:10.1002/2016WR018678.

Pannetier, R., Frampton, A., 2016. Air warming trends linked to permafrost warming in the sub-Arctic catchment of Tarfala, Sweden. Polar Research 35. doi:10.3402/polar.v35.28978.

Sjöberg, Y., Coon, E., Sannel, A.B.K., Pannetier, R., Harp, D., Frampton, A., Painter, S.L., Lyon, S.W., 2016. Thermal effects of groundwater flow through subarctic fens-A case study based on field observations and numerical modeling. Water Resources Research. doi:10.1002/2015WR017571.

Frampton, A., Destouni, G., 2015. Impact of degrading permafrost on subsurface solute transport pathways and travel times. Water Resources Research 51, 7680–7701. doi:10.1002/2014WR016689.

Dessirier, B., Frampton, A., Jarsjö, J., 2015. A global sensitivity analysis of two-phase flow between fractured crystalline rock and bentonite with application to spent nuclear fuel disposal. Journal of Contaminant Hydrology 182, 25–35. doi:10.1016/j.jconhyd.2015.07.006.

Frampton, A., 2014, Fracture transmissivity estimation using natural gradient flow measurements in sparsely fractured rock. In Fractured Rock Hydrogeology, International Association of Hydrogeologists (Sharp, J.M., Jr., and Troeger, U., eds.). doi:10.1201/b17016-10.

Dessirier, B., Jarsjö, J., Frampton, A., 2014. Modeling Two-Phase-Flow Interactions Across a Bentonite Clay and Fractured Rock Interface. Nuclear Technology. doi:10.13182/NT13-77.

Frampton, A., Painter, S.L., Destouni, G. 2013. Permafrost degradation and subsurface-flow changes caused by surface warming trends. Hydrogeology J, 21:271–280, doi: 10.1007/s10040-012-0938-z.

Sjöberg, Y., Frampton, A., Lyon, S.W. 2013. Using streamflow characteristics to explore permafrost thawing in northern Swedish catchments. Hydrogeology J, 21:271-280, doi: 10.1007/s10040-012-0932-5.

Cvetkovic, V. and Frampton, A. 2012, Solute transport and retention in three-dimensional fracture networks, Water Resour. Res., 48, W02509, doi:10.1029/2011WR011086.

Frampton, A., Painter, S., Sjöberg, Y, and Destouni, G., 2011, Transient modelling of permafrost dynamics in changing climate scenarios, 7th IEEE proceedings, PID2087089, 113-118, Stockholm, doi:10.1109/eScience.2011.24

Frampton, A., Painter, S., Lyon, S.W., and Destouni, G., 2011, Non-isothermal, three-phase simulations of near-surface flows in a model permafrost system under seasonal variability and climate change, Journal of Hydrology, 403, 352-359, doi: 10.1016/j.jhydrol.2011.04.010.

Frampton, A. and Cvetkovic, V., 2011, Numerical and analytical modeling of advective travel times in realistic three-dimensional fracture networks, Water Resour. Res., 47, W02506, doi:10.1029/2010WR009290.

Frampton, A. and Cvetkovic, V., 2010. Inference of field scale fracture transmissivities in crystalline rock using flow log measurements, Water Resour. Res., 46, W05506, doi: 10.1029/2009WR008367.

Fiori, A., Boso, F., de Barros, F.P.J., de Bartolo, S., Frampton, A., Severino, G., Suweis, S., Dagan, G., 2010. An Indirect Assessment on the Impact of Connectivity of Conductivity Classes upon Longitudinal Asymptotic Macrodispersivity, Water Resour. Res., 46, W11502, doi:10.1029/2009WR008590.

Cvetkovic, V. and Frampton, A., 2010. Transport and retention from single to multiple fractures in crystalline rock at Äspö (Sweden): 2. Fracture flow simulations and global retention properties, Water Resour. Res., 46, W05506, doi:10.1029/2009WR008030.

Frampton, A. and Cvetkovic, V., 2009. Significance of injection modes and heterogeneity on spatial and temporal dispersion of advecting particles in two-dimensional discrete fracture networks, Advances in Water Resources, 32, ADWR1301, doi: 10.1016/j.advwatres.2008.07.010.

Frampton, A. and Cvetkovic, V., 2007. Upscaling particle transport in discrete fracture networks: 2. Reactive tracers, Water Resour. Res., 43, W10429, doi:10.1029/2006WR005336.

Frampton, A. and Cvetkovic, V., 2007. Upscaling particle transport in discrete fracture networks: 1. Nonreactive tracers, Water Resour. Res., 43, W10428, doi:10.1029/2006WR005334.

Landeryou, M., Eames, I., Frampton, A., Cottenden, A.M., 2004. Modelling strategies for liquid spreading in medical absorbents. International Journal of Clothing Science and Technology 16, 163–172, doi:10.1108/09556220410520441

Eames, I., Small, I., Frampton, A., Cottenden, A.M., 2003. Experimental and theoretical study of the spread of fluid from a point source on an inclined incontinence bed-pad. Journal of Engineering in Medicine 217, 263–271, doi:10.1243/095441103322060712

Landeryou, M., Cottenden, A., Eames, I., Frampton, A., 2003. Bulk Liquid-transport Properties of Multi-layered Fibrous Absorbents. Journal of the Textile Institute 94, 67–76, doi:10.1080/00405000308630629.

 

Monographs

Frampton, A., 2010. Stochastic analysis of fluid flow and tracer pathways in crystalline fracture networks. Doctoral Thesis, KTH. US AB, Stockholm, Sweden. ISBN 978-91-7415-560-0. ISSN 1650-8602. ISRN KTH/LWR/PHD 1056-SE. TRITA LWR PhD 1056. Link

 

Technical reports

Frampton, A., Gotovac, H., Holton, D., Cvetkovic, V., 2015. Äspö Task Force on modelling of groundwater flow and transport of solutes. Task 7 – Subsurface flow and transport modelling of hydraulic tests and in situ borehole flow measurements conducted at Olkiluoto Island (No. P-13-42). Swedish Nuclear Fuel and Waste Management Co (SKB), Stockholm.

Frampton, A., Cvetkovic, V., and Holton, D., 2009. Äspö Task Force on modelling of groundwater flow and transport of solutes – Task 7A. Task 7A1 and 7A2: Reduction of performance assessment uncertainty through modelling of hydraulic tests at Olkiluoto, Finland. International Technical Document ITD-09-05. Svensk Kärnbränslehantering AB, Stockholm, Sweden.

 

Book reviews

Frampton, A., 2014. P. M. Adler, J.-F. Thovert, V. V. Mourzenko: Fractured Porous Media: Oxford University Press, 2013, pp. 175. Mathematical Geosciences 46, 771–773. doi:10.1007/s11004-014-9527-0

 

Open access computer programs

Frampton, A., Dessirier, B., Pannetier, R., 2014. Visual PyFlow – an open-source graphical solver of the groundwater flow equation. Available at https://bitbucket.org/Visual_PyFlow.

 

Selected contributions at scientific conferences and workshops

Frampton, A., Pannetier, R., Destouni, G. 2016. Mechanisms governing solute transport in the active layer of coupled permafrost-hydrogeological systems. Presented at the 11th International Conference on Permafrost, Potsdam, Germany.

Schuh, C., Frampton, A., Christiansen, H.H., 2016. Soil moisture redistribution and effect on active layer response to temperature variations in a dry loess terrace in Adventdalen, Svalbard. Presented at the 11th International Conference on Permafrost, Potsdam, Germany.

Pannetier, R., Frampton, A., 2016. Analysis of Flow Pathways and Transport Times in a Periglacial Permafrost Catchment near Kangerlussuaq, Greenland. Presented at the 11th International Conference on Permafrost, Potsdam, Germany.

Grenier, C., Anbergen, H., Bense, V., Coon, E., Collier, N., Costard, F., Ferry, M., Frampton, A., others, 2016. The InterFrost benchmark of Thermo-Hydraulic codes for cold regions hydrology – first intercomparison phase results. Presented at the 11th International Conference on Permafrost, Potsdam, Germany.

Frampton, A., Destouni, G., 2016. Solute transport modelling in a coupled water and heat flow system applied to cold regions hydrogeology, in: EGU General Assembly Conference Abstracts. p. 15497.

Frampton, A., 2016. Groundwater flow and solute transport modelling in coupled permafrost-hydrogeological systems. Presented at the 32nd Nordic Geological Winter Meeting, Helsinki, Finland.

Ströberg, A., Ebert, K., Jarsjö, J., Frampton, A., 2016. Contaminated area instability – the example of Ångerman River, northern Sweden. Presented at the 32nd Nordic Geological Winter Meeting, Helsinki, Finland.

Frampton, A., Pannetier, R., Destouni, G., 2015. Modelling groundwater transport and travel times in warming permafrost. Presented at the Grundvattendagarna, Sveriges Geologiska Undersökning, Göteborg, Sweden.

Grenier, et al., 2015. The InterFrost benchmark of Thermo-Hydraulic codes for cold regions hydrology – first inter-comparison results, in: Geophysical Research Abstracts. Presented at the EGU General Assembly, Vienna, 9723.

Pannetier, R., Frampton, A., 2015. Transient modeling of the hydro-thermal state of frozen ground in the sub-arctic catchment of Tarfala, Sweden., in: Geophysical Research Abstracts. Presented at the EGU General Assembly, Vienna, 11471.

Sjöberg, Y., Lyon, S., Pannetier, R., Coon, E., Harp, D., Frampton, A., Painter, S., 2015. Thermal effects from groundwater flow-A case study from a subarctic fen within the sporadic permafrost zone of Tavvavuoma, Sweden, in: Geophysical Research Abstracts. Presented at the EGU General Assembly, Vienna, 14029.

Frampton, A., 2015. Impact of thawing ground on subsurface water flow and transport in a modelled permafrost system, in: Geophysical Research Abstracts. Presented at the EGU General Assembly, Vienna, 11787.

Frampton, A., Destouni, G., Pannetier, R., 2014. Changes in travel times in thawing permafrost systems. Presented at the AGU Fall Meeting, San Francisco, C11C–0386.

Frampton, A., Destouni, G., 2014a. Modelling permafrost-induced hydrological change and associated changes in solute transport across scales, in: Geophysical Research Abstracts. Presented at the EGU General Assembly, Vienna, 10837.

Frampton, A., Destouni, G., 2014b. Impact of hydro‐climatic variability and change on travel time distributions in modelled active layer systems. Presented at the EUCOP4, Evora, Portugal, EUCOP4–0385.

Frampton, A., Destouni, G., 2013. Changes in subsurface water residence times under permafrost formation and degradation dynamics subject to hydro-climatic variability and change. Presented at the EGU General Assembly, Geophysical Research Abstracts, Vienna, EGU2013–5038.

Frampton, A., Painter, S.L., Destouni, G., 2012. Effects of hydrological inputs on the dynamics of permafrost system formation and degradation, in: Geophysical Research Abstracts. Presented at the EGU General Assembly, Vienna, EGU2012–5204–1.

Frampton, A., Cvetkovic, V., 2012. Modelling flow and transport in sparsely fractured rock using flow log data, in: International Association of Hydrogeologists. Presented at the Groundwater in Fractured Rocks Conference, Prague.

Frampton, A., 2012. Modelling groundwater flow in partially frozen media. Presented at the Hydro-Perm Workshop, Longyearbyen, Svalbard.

Frampton, A., Destouni, G., Sjoberg, Y., Painter, S., 2011. Transient modeling of permafrost dynamics in changing climate scenarios, in: E-Science, 2011 IEEE 7th International Conference. 113–118.

Frampton, A., Painter, S.L., Lyon, S.W., Sjöberg, Y., Destouni, G., 2011. Transient modeling of permafrost dynamics in a changing climate. Presented at the AGU Fall Meeting, San Francisco, C53G–02.

Frampton, A., Cvetkovic, V., 2011. Modelling sparsely fractured rock using flow log data. Presented at the Deep Hydrogeology Workshop, Department of Earth Sciences, Uppsala University, Sweden.

Frampton, A., Painter, S.L., Lyon, S.W., Destouni, G., 2011. Non-isothermal, three-phase simulations of near-surface flows in a model permafrost system under seasonal variability and climate change, in: Geophysical Research Abstracts. Presented at the EGU General Assembly, Vienna, EGU2011–8916.

 

 

Publications

A selection from Stockholm University publication database
  • 2015. Andrew Frampton, Georgia Destouni. Water resources research 51 (9), 7680-7701

    Subsurface solute transport under surface warming and degrading permafrost conditions is studied using a physically based model of coupled cryotic and hydrogeological flow processes combined with a particle tracking method. Changes in the subsurface water and inert solute pathways and travel times are analyzed for different modeled geological configurations. For all simulated cases, the minimum and mean travel times increase nonlinearly with warming irrespective of geological configuration and heterogeneity structure. The timing of the start of increase in travel time depends on heterogeneity structure, combined with the rate of permafrost degradation that also depends on material thermal and hydrogeological properties. The travel time changes depend on combined warming effects of: i) increase in pathway length due to deepening of the active layer, ii) reduced transport velocities due to a shift from horizontal saturated groundwater flow near the surface to vertical water percolation deeper into the subsurface, and iii) pathway length increase and temporary immobilization caused by cryosuction-induced seasonal freeze cycles.

  • 2012. Andrew Frampton, Scott L. Painter, Georgia Destouni. Hydrogeology Journal 21 (1), 271-280

    Change dynamics of permafrost thaw, andassociated changes in subsurface flow and seepage into surface water, are analysed for different warming trends in soil temperature at the ground surface with a three-phase two-component flow system coupled to heat transport. Changes in annual, seasonal and extreme flows are analysed for three warming-temperature trends, representing simplified climate change scenarios. The results support previous studies of reduced temporal variability of groundwater flow across all investigated trends. Decreased intra-annual flow variability may thus serve asan early indicator of permafrost degradation before longer term changes in mean flows are notable. This is advantageous since hydrological data are considerably easier to obtain, may be available in longer time series, and generally reflect larger-scale conditions than direct permafrost observations. The results further show that permafrost degradation first leads to increasing water discharge, which then decreases as the permafrost degradation progresses further to total thaw. The most pronounced changes occur for minimum annual flows. The configuration considered represents subsurface discharge from a generic heterogeneous soil-type domain.

  • 2011. Andrew Frampton (et al.). Journal of Hydrology 403 (3-4), 352-359

    Permafrost responses to a changing climate can affect hydrological and biogeochemical cycling, ecosystems and climate feedbacks. We have simulated a model permafrost system in the temperature range associated with discontinuous permafrost focusing on interactions between permafrost and hydrology using a non-isothermal, three-phase model of water migration coupled to heat transport in partially frozen porous media. We explore the subsurface hydraulic property controls on the formation and dynamics of permafrost, and how this impacts seasonal variability of subsurface runoff to surface waters. For all subsurface conditions considered, the main common hydrological signal of permafrost degradation in a warming trend is decreasing seasonal variability of water flow. This is due to deeper and longer flow pathways with increasing lag times from infiltration or thawing through subsurface flow to surface water discharge. These results show how physically based numerical modelling can be used to quantitatively and qualitatively improve the understanding of how permafrost thawing relates to, and may be detected in, hydrological data. This is advantageous since hydrological data is considerably easier to obtain, may be available in longer time series, and generally reflects larger-scale conditions than direct permafrost observations.

  • 2011. Andrew Frampton, Vladimir Cvetkovic. Water resources research 47, W02506

    Travel time distributions obtained from advective transport in multiple realizations of realistic discrete fracture network simulations are analyzed using the truncated one-sided stable distribution, which has previously been shown to generalize both the advectiondispersion solution as well as one-sided stable distributions. Using this model, it is shown that the Fickian assumption inherent in the advection-dispersion equation generally fails, despite the first two moments of travel time essentially scaling linearly with distance. It is also observed that the equally probable realizations drawn from the ensemble can produce a wide range of behavior under the current configuration, such that Fickian conditions are almost obtained in some cases for increasing scales. On the basis of a small-scale calibration against particle breakthrough, the model is then shown to successfully predict limiting bounds of transport for a one order of magnitude increase in scale. Correlation in particle velocity is explicitly shown to be significant for scales close to the characteristic Lagrangian segment length. The network configuration is obtained from extensive site characterization data at the Laxemar region in Sweden and represents a block-scale domain of reasonably sparse background fractures.

  • 2010. V. Cvetkovic, A. Frampton. Water resources research 46, W05506

    Hydrogeologic characterization of crystalline rock formations on the field scale is important for many applications but still presents a multitude of challenges. In this work we use comprehensive hydrostructural information and present a detailed simulation study of flow and advective transport in a discrete fracture network (DFN) that replicates the Tracer Retention Understanding Experiments (TRUE) Block Scale rock volume at the Aspo Hard Rock Laboratory (Sweden). Simulated water residence time tau and hydrodynamic retention parameter beta are used as independent constraints for estimating material retention properties as presented in paper 1 of this series, whereas simulated mean water residence times are compared with observed values. We find that the DFN simulations reproduce water residence times reasonably well, indicating that the characterization data are sufficient and that the DFN model does capture dominant features of the flow paths analyzed. The empirical quadratic law that relates aperture and transmissivity seems to better reproduce calibrated mean water residence times than the theoretical cubic law for the five flow paths. The active specific surface area (beta/tau) [1/L] as inferred from simulations is used for defining a generic retention model for the dominant rock type (Aspo diorite) that matches fairly well the entire range of calibrated retention parameters of the TRUE tests. The combination of paper 1 and this work provides a general, comprehensive methodology for evaluating tracer test results in crystalline rock where a comparable amount of information is available; critical to this methodology is that tracer tests are carried out using tracers with sufficiently different sorption affinities (of factor 10-100).

  • 2009. A. Frampton, V. Cvetkovic. Advances in Water Resources 32 (5), 649-658
  • 2007. A. Frampton, V. Cvetkovic. Water resources research 43 (10), W10429
  • 2015. Benoît Dessirier, Andrew Frampton, Jerker Jarsjö. Journal of Contaminant Hydrology 182, 25-35

    Geological disposal of spent nuclear fuel in deep crystalline rock is investigated as a possible long term solution in Sweden and Finland. The fuel rods would be cased in copper canisters and deposited in vertical holes in the floor of deep underground tunnels, embedded within an engineered bentonite buffer. Recent experiments at the Äspö Hard Rock Laboratory (Sweden) showed that the high suction of unsaturated bentonite causes a de-saturation of the adjacent rock at the time of installation, which was also independently predicted in model experiments. Remaining air can affect the flow patterns and alter bio-geochemical conditions, influencing for instance the transport of radionuclides in the case of canister failure. However, thus far, observations and model realizations are limited in number and do not capture the conceivable range and combination of parameter values and boundary conditions that are relevant for the thousands of deposition holes envisioned in an operational final repository.

    In order to decrease this knowledge gap, we introduce here a formalized, systematic and fully integrated approach to study the combined impact of multiple factors on air saturation and dissolution predictions, investigating the impact of variability in parameter values, geometry and boundary conditions on bentonite buffer saturation times and on occurrences of rock de-saturation. Results showed that four parameters consistently appear in the top six influential factors for all considered output (target) variables: the position of the fracture intersecting the deposition hole, the background rock permeability, the suction representing the relative humidity in the open tunnel and the far field pressure value. The combined influence of these compared to the other parameters increases as one targets a larger fraction of the buffer reaching near-saturation. Strong interaction effects were found, which means that some parameter combinations yielded results (e.g., time to saturation) far outside the range of results obtained by the rest of the scenarios. This study also addresses potential air trapping by dissolution of part of the initial air content of the bentonite, showing that neglecting gas flow effects and trapping could lead to significant underestimation of the remaining air content and the duration of the initial aerobic phase of the repository.

Show all publications by Andrew Frampton at Stockholm University

Last updated: June 25, 2018

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