Mass Transfer & Porous Media (MTPM) - Andra

P/MTPM/16ModelIrmayvG-M1vG-M2vG-M3Table 1: Summary of estimated parameters from the five testsK s (m/d) m α (m -1 ) φmean SD CV mean SD CV mean SD CV Mean SD CV4.98·10 -96.61·10 -96.77·10 -96.87·10 -9 3.56·10 -91.43·10 -91.47·10 -91.17·10 -9 0.070.220.220.170.2660.7731.8130.5940.0680.2650.2040.2590.250.340.110.441.44·10 -39.30·10 -49.09·10 -41.01·10 -3 2.43·10 -43.77·10 -43.54·10 -42.48·10 -4 0.170.410.390.250.4210.4220.4250.421( K s is saturated conductivity; m and α are parameters defining the retention curve; φ is porosity)0.0130.0170.0140.0160.030.040.030.04were computed from values estimated in the five infiltration experiments. Irmay model has one moreparameter ( n r ) than other models and its mean, standard deviation and coefficient of variation are 3.03,0.432 and 0.14, respectively.Although the computed values of the objective functions and the model selection criteria are various fromdata to data, the overall evaluations of the results indicate that even though Irmay model has a better fit tothe observation data, the general van Genutchten model (vG-M1) is the best model for the relativeconductivity, since it minimizes the three model selection criteria. The better fit from Irmay model maycome from the fact that it estimates more parameters. The uncertainty from the inverse modeling whichinvolves more parameters is usually much larger than those with few parameters. From the point of modelparsimony, the other two van Genutchten models (vG-M2 and vG-M3) with more complex functionstructures are not the attractive alternates for the general van Genutchten model, even though they havevery similar performance. Therefore, we identify the general van Genutchten function as the best modelfor water flow and solute transport in the unsaturated compacted bentonite.ACKNOWLEDGMENTS:This work was supported by the Spanish Nuclear Waste Company (ENRESA) within the framework of theFEBEX Research Project through a Research Grant signed with the University of La Coruña. The FEBEXProject as a whole has been funded by the European Union through research contracts FI4W-CT95-0006and FIKW-CT-2000-00016 of the Nuclear Fission Safety Program.ReferencesDai, Z., and Samper, J., Inverse problem of multicomponent reactive chemical transport in porous media:Formulation and applications: Water Resour. Res. , v. 40, p. W07407, doi: 10.1029/2004WR003248,2004.Huertas, F., J. L. Fuentes-cantillana, F. Jullien, P. Rivas, J. Linares, P. Fariña, M. Ghoreychi, N. Jockwer,W. Kickmaier, M. A. Martínez, J. Samper, E. Alonso and F. J. Elorza, Full-scale engineered barriersexperiment for a deep geological repository for high-level radioactive waste in crystalline host rock(FEBEX project), Final report, EUR 19147, European Communities, 362 pp., 2000.Irmay, S., On the hydraulic conductivity of saturated soils, Trans. Amer. Geophys. Union 35, 463-468,1954.Van Genuchten, M. Th, A closed-form for predicting the hydraulic conductivity of unsaturated soils, SoilSci. Soc. Am. J . 44:892-898, 1980Page 454INTERNATIONAL MEETING, SEPTEMBER 17...>...18, 2007, LILLE, FRANCECLAYS IN NATURAL & ENGINEERED BARRIERSFOR RADIOACTIVE WASTE CONFINEMENT