3rd DECOVALEX 2011 workshop, 21th of April 2009, , Gyeongju, Korea Concluding discussions on work to date B. Garitte and A. Gens (CIMNE – UPC) Dept. of Geotechnical Engineering and Geosciences TECHNICAL UNIVERSITY OF CATALONIA (UPC)

Index (T)H(M) formulation Parameters and constitutive equations Model setup Comparison of the modelling results Relative humidity (boundary condition) Water balance Pore water pressure Water content Strain Summary of the mechanisms Conclusion

(T)H(M) formulation Main balance equation: water mass balance Variation of the water mass in a certain volume (variation of liquid density, gas density, water saturation, gas saturation and porosity) In- and outflux of water to/from that volume (flux of water in the liquid phase and flux of water in the gas phase) Source and sink terms CAS CEA JAEA Quintessa UoE Energy balance Stress equilibrium Air mass balance

(T)H(M) formulation Main balance equation: water mass balance Variation of the water mass in a certain volume (variation of liquid density, gas density, water saturation, gas saturation and porosity) In- and outflux of water to/from that volume (flux of water in the liquid phase and flux of water in the gas phase) Source and sink terms CAS CEA JAEA Quintessa UoE Energy balance Stress equilibrium Air mass balance

(T)H(M) formulation Main balance equation: water mass balance Variation of the water mass in a certain volume (variation of liquid density, gas density, water saturation, gas saturation and porosity) In- and outflux of water to/from that volume (flux of water in the liquid phase and flux of water in the gas phase) Source and sink terms CAS CEA JAEA Quintessa UoE Energy balance Stress equilibrium Air mass balance

(T)H(M) formulation Main balance equation: water mass balance Variation of the water mass in a certain volume (variation of liquid density, gas density, water saturation, gas saturation and porosity) In- and outflux of water to/from that volume (flux of water in the liquid phase and flux of water in the gas phase) Source and sink terms CAS CEA JAEA Quintessa UoE Energy balance Stress equilibrium Air mass balance

(T)H(M) formulation Main balance equation: water mass balance Variation of the water mass in a certain volume (variation of liquid density, gas density, water saturation, gas saturation and porosity) In- and outflux of water to/from that volume (flux of water in the liquid phase and flux of water in the gas phase) Source and sink terms CAS CEA JAEA Quintessa UoE Bishop effective stress Energy balance CAS CEA JAEA Quintessa UoE Stress equilibrium CAS CEA JAEA Quintessa UoE Stiffness against suction Air mass balance CAS CEA JAEA Quintessa UoE

Parameters and constitutive equations Step 0 CAS CEA JAEA Quint. UoE Physical Solid grain density ρs [kg/m3] 2710   2710  2700   Porosity φ 0.165   0.16  0.162 Hydraulic Intrinsic permeability k [m2]  7.5E-20 2E-20  2E-20  1.69E-19 1.9E-20  Dynamic viscosity μ [Pa.s] 1E-3 2.9E-4 Liquid relative permeability λ’  0.4  0.68  0.65 0.3  Vapour diffusion coefficient  6E-6 5E-6  Mechanical Young modulus E [GPa]  6 1.5 Poisson coefficient ν  0.27  0.3 Friction angle φ [º] Cohesion c [MPa] Hydro-Mech. coupling Suction bulk modulus Ks [GPa] Air entry value (retention curve) P0 [MPa]  3.9  8 Shape parameter (retention curve) λ 0.128  0.15 Maximum suction (retention curve)* Ps [MPa] 700 Second shape parameter (retention curve)* λs  2.73 2.73  Residual and maximum saturation (retention curve) Srl – Srs  0 – 1  0 - 1 * Modified Van Genuchten

Parameters and constitutive equations Step 1 CAS CEA JAEA Quint. UoE Physical Solid grain density ρs [kg/m3] 2710   2710  2700   Porosity φ 0.165   0.16  0.162 Hydraulic Intrinsic permeability k [m2]  7.5E-20 1E-19  2E-20  1.13E-19 1.9E-20  Dynamic viscosity μ [Pa.s] 1E-3 2.9E-4 Liquid relative permeability λ’  0.4  0.65 0.3  Vapour diffusion coefficient  6E-6  ? 5E-6  Mechanical Young modulus E [GPa]  6  1 1.5 Poisson coefficient ν  0.27  0.3 Friction angle φ [º] Cohesion c [MPa] Hydro-Mech. coupling Suction bulk modulus Ks [GPa]  1.1E-4**  dif. Air entry value (retention curve) P0 [MPa]  3.9  8 Shape parameter (retention curve) λ 0.128  0.15 Maximum suction (retention curve)* Ps [MPa] 700 Second shape parameter (retention curve)* λs  2.73 2.73  Residual and maximum saturation (retention curve) Srl – Srs  0 – 1  0 - 1 * Modified Van Genuchten ** Moisture swelling coeff. [-] (Not defined in report)

Parameters and constitutive equations Water retention curve

Parameters and constitutive equations Dependency of permeability on saturation

Parameters and constitutive equations Dependency of permeability on saturation

Model setup Isotropic conditions σ =3.2MPa, pw =1.21MPa 1.21MPa 3.2MPa Plane strain 0-flow on all borders, excepted on top Isothermal (T=15º) 130m 1.85MPa 4.9MPa 2.49MPa 6.6MPa pw σ 130m

Model setup Application of Relative Humidity 1.3m σ =3.2MPa, pw =1.21MPa 1.21MPa 3.2MPa Plane strain 0-flow on all borders, excepted on top Isothermal (T=15º) 130m 1.85MPa 4.9MPa 2.49MPa 6.6MPa pw σ 130m

Comparison of the modelling results Relative humidity (boundary condition) Model: at MT wall Measurements: in the MT

Comparison of the modelling results Relative humidity (boundary condition) 2cm inside

Comparison of the modelling results Relative humidity 25 - 27cm inside

Comparison of the modelling results Relative humidity 35cm inside Only 3 measurements are usable Measurements equal at 35cm and at 27cm Lack of measurements between 2 and 25cm

Comparison of the modelling results Water balance

Comparison of the modelling results Pore water pressure Measurements Inconsistent measurements (according to our models) Number of sensors in suction (determination of suction limit, but…)

Comparison of the modelling results Pore water pressure Between 1.8 and 2.1m

Comparison of the modelling results Pore water pressure Between 1.8 and 2.1m

Comparison of the modelling results Pore water pressure Between 1.8 and 2.1m Effect of the instrumentation? Type of sensor No Measuring principle Boreholes Filling material In-borehole Pore Pressure System 4 Piezo-resistive (piezometer) BVE-1 Cement-bentonite Mini- piezometer 24 32 Resin Humidity 16 Psychrometer Cement-resin Capacitive 14 Mini-extensometer 8 Potentiometer None Electrode rods 4 + Surf. Resistance Change Compacted rock powder TDR 10 ¿Resin? MH coupling?

Comparison of the modelling results Pore water pressure Initial conditions

Comparison of the modelling results Pore water pressure

Comparison of the modelling results Pore water pressure

Comparison of the modelling results Pore water pressure

Comparison of the modelling results Pore water pressure

Comparison of the modelling results Water content Initial conditions

Comparison of the modelling results Water content porosity wcon [%] 0.14 6.03 0.15 6.54 0.16 7.05 0.17 7.59 0.18 8.13 BVE85: 104kg BVE86: 858kg

Comparison of the modelling results Strain

Comparison of the modelling results Strain

Summary of the mechanisms Evaporation Desaturation Dominant water transport mode: vapour diffusion in the gas phase (non advective) Reduction of the permeability Dominant water transport mode: Darcy flow in the liquid phase (advective)

Summary of the mechanisms Quintessa

Summary of the mechanisms Quintessa

Conclusions Task A is largely on schedule… Thank you for your efforts. Globally good results, but improvements are required. Sensitivity analysis is advised before starting with advanced modelling in step 2. Step 2 will be: advanced HM modelling making a blind prediction of phase II using the calibration from phase I. Suggested additional features (non inclusive): Anisotropy (permeability, stress state) Work on initial conditions Damage Try to explain the “inconsistent” set of pore water pressure measurements The fast pore water pressure response. Modelling the instrumentation boreholes (one of them)? MH coupling? Do not forget the deadline for the internal report on step 0. Article for the TT conference will be built on that basis. Try to deliver your results on time!