01.01.2014  Original Paper  Ausgabe 1/2014 Open Access
Modeling of Coupled ThermoHydroMechanical Processes with Links to Geochemistry Associated with BentoniteBackfilled Repository Tunnels in Clay Formations
 Zeitschrift:
 Rock Mechanics and Rock Engineering > Ausgabe 1/2014
1 Introduction
2 ThermalElastoPlastic BBM in TOUGHFLAC
2.1 ThreeDimensional Yield Surface
2.2 Stress State
2.3 Strains Due to Stress, Temperature and Suction
2.3.1 Elastic Strain
2.3.2 Plastic Strain
2.3.3 Thermal Strain
2.3.4 Suction Strain
3 THM Model Setup and Simulation Sequence
Parameter  Value/function 

Initial dry density, ρ
_{d} (kg/m^{3})  1.6·10^{3}

Initial porosity, ϕ (−)  0.41 
Saturated permeability, k (m^{2})  2.0·10^{−21}

Relative permeability, k
_{r} (−) 
\(k_{\text{rl}} = S_{\text{l}}^{3}\)

Van Genuchten parameter, P
_{VG} (MPa)  30 
(van Genuchten 1980) parameter, λ
_{VG} (−)  0.32 
Thermal expansion, β (1/ °C)  1.5 × 10^{−4}

Dry specific heat, C
_{s} (J/kg °C) 
\(c_{\text{s}} = 1.38{\kern 1pt} \,{\text{T}} + 732.5\)

Thermal conductivity, λ
_{m} (W/mK) 
\(\lambda_{\text{m}} = 1.28  \frac{0.71}{{1 + e^{{{{\left( {S_{\text{l}}  0.65} \right)} \mathord{\left/ {\vphantom {{\left( {S_{\text{l}}  0.65} \right)} {0.1}}} \right. \kern0pt} {0.1}}}} }}\)

Effective molecular diffusion coefficient, D
_{v} (m^{2}/s) 
\(D_{\text{v}} = 2.16e  5 \times \tau \times \varphi \times S_{\text{g}} \left( {\frac{{T_{\text{abs}} }}{273.8}} \right)^{1.8}\)

Mass flow times tortuosity factor, τ (−)  0.8 
Parameter  Value 

Compressibility parameter for stressinduced elastic strain, κ
_{PS0} (−)  0.05 
Compressibility parameter for suctioninduced elastic strain, κ
_{SP0} (−)  0.25 
Shear modulus, G (MPa)  NA 
Poisson’s ratio, ν (−)  0.4 
Parameter for suctioninduced elastic strain, α
_{SS} (−)  0 
Parameter for stressinduced strain α
_{PS} (MPa^{−1})  −0.003 
Parameter for stressinduced strain, α
_{SP} (−)  −0.161 
Reference stress state for relating elastic compressibility to suction, P
_{ref} (MPa)  0.5 
Parameters that relate elastic volumetric strain and temperature changes, α
_{0} (°C^{−1})  1.5e − 4 
Compressibility parameter in virgin soil states at zero suction, λ
_{PS0} (−)  0.15 
Parameter defining soil stiffness associated with loading collapse yield, r
_{λ} (−)  0.925 
Parameter for the increase of soil stiffness with suction, β
_{λ} (MPa^{−1})  0.1 
Parameter that relates cohesion to temperature, ρ
_{s} (°C^{−1})  0 
Parameter describing the increase of cohesion with suction, k
_{s} (−)  0.1 
Tensile strength at saturated conditions, P
_{S0} (MPa)  0 
A reference stress state for compressibility relation in virgin states, P
^{C} (MPa)  0.5 
Slope of the critical state line, M (−)  1 
Nonassociativity parameter in the plasticity flow rule, α
_{a} (−)  0.53 
Specific volume at reference stress states P
^{C} in virgin states, v
^{c} (−)  1.937 
Net mean yield stress for saturated conditions at reference temperature, P
_{0T}
^{*}
(MPa)  12.0 
Parameter  Value 

Bulk density (kg/m^{3})  2,400 
Matrix porosity (–)  0.15 
Young’s modulus (GPa)  5 
Poisson’s ratio (–)  0.3 
Specific heat (J/kg °C)  900 
Thermal conductivity (W/mK)  2.2 
Thermal expansion coefficient (°C^{−1})  1.0 × 10^{−5}

Permeability (m^{2})  5.0 × 10^{−20}

Biot’s effective stress parameter  1.0 
Van Genuchten water retention parameter, m
 0.41 
Van Genuchten water retention parameter, P
_{0} (MPa)  48 
Bulk modulus, K (GPa)  4.17 
Shear modulus, G (GPa)  1.92 
Cohesion, C (MPa)  5 
Friction angle (°)  25° 
Dilation angle (°)  10° 
Tensile strength (MPa)  1.0 
Joint cohesion (MPa)  2.2 
Joint friction (°)  23° 
Joint tensile strength (MPa)  0.5 