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laws:acmeg
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ACMEG
Description
Elasto-plastic constitutive law for saturated soils under non-isothermal conditions with two plastic mechanisms.
It can take into account :
- linear or non-linear thermo-elasticity
- the progressive plasticity inside the yield limit
- the elasto-plasticity and thermo-plasticity
- the critical state concept
- the cyclic behaviour through the isotropic plastic mechanism
- The suction effect on the evolution of pre-consolidation pressure (LC)
This constitutive model for unsaturated soil is developed based on the generalized effective stress framework (Bishop’s effective stress). So, if unsaturated states are considered (ISUC=1), the Bishop’s effective stress must be used (ISOL=7). Moreover, this mechanical constitutive model may be coupled with retention law 17 or 18 in WAVAT (ISRW=17 or 18).
The model
This law is used for mechanical analysis of elasto-plastic saturated and unsaturated porous media undergoing large strains under non-isothermal conditions with possible cyclic isotropic loadings.
Files
Prepro: LACMEG.F
Lagamine: PIL_ACMEG2D.F, PIL_ACMEG3D.F
Availability
| Plane stress state | NO |
| Plane strain state | YES |
| Axisymmetric state | YES |
| 3D state | YES |
| Generalized plane state | NO |
Input file
Parameters defining the type of constitutive law
| Line 1 (2I5, 60A1) | |
|---|---|
| IL | Law number |
| ITYPE | 599 |
| COMMNT | Any comment (up to 60 characters) that will be reproduced on the output listing |
Integer parameters
| Line 1 (3I5) | |
|---|---|
| NINTV | Number of sub-steps used to integrate numerically the constitutive equation in a time step |
| = 0 : Number of sub-steps is based on the norm of the deformation increment and on DIV | |
| ISOL | = 0 : Use of total stresses in the constitutive law |
| ≠ 0 : Use of effective stresses or independent stress variables in the constitutive law (See appendix 8) | |
| ITHERMO | = 0 : Isothermal computation, the five real parameters related to thermal effect will not be taken into account |
| = 1 : Non-isothermal computation, a THM analyse must be done | |
| = 2 : Non-isothermal analyses with a constant volumetric thermal dilatation coefficient | |
| ISUC | = 0 : Saturated computation, the last two real parameters will not be taken into account |
| = 1 : Unsaturated computation, the Bishop’s effective stress must be used (ISOL=7) | |
| NUMRET | $\in$ [0,18] : Number of the retention curve used in the WAVAT diffusive law |
Real parameters
| Line 1 (7G10.0) | |
|---|---|
| XKREF | Bulk modulus at reference pressure (PREF) |
| XGREF | Shear modulus at reference pressure (PREF) |
| PREF | Reference pressure for which the elastic modulus are defined |
| XN | Elastic exposant |
| PHI | Friction angle at critical state |
| BETA | Beta coefficient related to the slope of the consolidation line |
| ALPHA | Material parameter to enable a non-associated flow rule |
| Line 2 (5G10.0) | |
| A | Material parameter defining the evolution of the degree of mobilisation of the deviatoric mechanism |
| B | Material parameter defining the shape of the deviatoric yield limit |
| C | Material parameter defining the evolution of the degree of mobilisation of the isotropic mechanism |
| D | Distance between critical state line and the consolidation line in a logarithmic scale (pre-consolidation pressure = critical pressure * D) |
| PCI | Initial critical pressure |
| Line 3 (4G10.0) | |
| RAYELAD | Ratio between the extreme deviatoric yield limit and the initial deviatoric elastic domain |
| RAYELAI | Ratio between the extreme isotropic yield limit and the initial isotropic elastic domain |
| DIV | Size of sub-steps for computation of NINTV (if NINTV=0; Default value=5.D-3) |
| RHOS | Density of solid phase |
| Line 4 (5G10.0) | |
| TDILAS | Coefficient of thermal dilatation of the solid skeleton |
| XNTEM | Thermo-elastic exponent |
| DEV | Parameter for the evolution of the friction angle with temperature |
| GAMAT | Parameter for the evolution of the pre-consolidation pressure with temperature |
| TEMP0 | Temperature for which the pre-consolidation pressure is defined |
| Line 5 (2G10.0) | |
| GAMAS | Parameter for the evolution of the pre-consolidation pressure with suction |
| OMEGA | Parameter for the evolution of the plastic compressibility with suction |
| Line 6 (7G10.0) | |
| ALPHABIO | Coefficient of biological dilatation of the solid skeleton |
| AKDMKG | (kd-kg) coefficient for the variation of porosity with concentration |
| AKHI | Multiplier factor for the concentration effect (bio + precipitation) |
| AKDM | Coefficient of linear attachement |
| OMEGAC | Effect of concentration on the plastic compressibility |
| GAMAC | Parameter for the evolution of the pre-consolidation pressure with concentration |
| CMIN | Minimal concentration to modify the pre-consolidation pressure |
| Line 7 (1G10.0) | |
| GC | Parameter for the evolution of the friction angle with concentration |
Stresses
Number of stresses
6 for 3D analysis
4 for 2D plane strain and axisymmetric analysis
Meaning
The stresses are the components of CAUCHY stress tensor in global (X,Y,Z) coordinates.
For the 3-D state:
| SIG(1) | $\sigma_{xx}$ |
| SIG(2) | $\sigma_{yy}$ |
| SIG(3) | $\sigma_{xy}$ |
| SIG(4) | $\sigma_{zz}$ |
| SIG(5) | $\sigma_{xz}$ |
| SIG(6) | $\sigma_{yz}$ |
For the other cases:
| SIG(1) | $\sigma_{xx}$ |
| SIG(2) | $\sigma_{yy}$ |
| SIG(3) | $\sigma_{xy}$ |
| SIG(4) | $\sigma_{zz}$ |
State variables
Number of state variables
20
List of state variables
| Q(1) | Element thickness |
| = 1 : Plane strain state | |
| = circumferential strain rate ($\dot{\varepsilon}_{\theta}$) in axisymmetrical state | |
| = 0 : 3D state | |
| Q(2$\rightarrow$7) | Total strains |
| Q(2) | EPSxx |
| Q(3) | EPSyy |
| Q(4) | EPSzz |
| Q(5) | EPSxy |
| Q(6) | EPSxz (= 0 in plane strains and axisymmetric analyses) |
| Q(7) | EPSyz (= 0 in plane strains and axisymmetric analyses) |
| Q(8) | RAY(1) = Radius of the deviatoric mechanism |
| Q(9) | RAY(2) = Radius of the isotropic mechanism |
| Q(10) | IPEL(1) = Activity of the deviatoric mechanism |
| = 1 : The deviatoric mechanism is active | |
| = -1 : The deviatoric mechanism is non-active | |
| Q(11) | IPEL(2) = Activity of the isotropic mechanism |
| = 1 : The isotropic mechanism is active | |
| = -1 : The isotropic mechanism is non-active | |
| Q(12) | EPSVP = Volumetric plastic strain |
| Q(13) | PRECONS = Pre-consolidation pressure |
| Q(14) | LAMDA(1) = Plastic multiplier of the deviatoric mechanisms |
| Q(15) | LAMDA(2) = Plastic multiplier of the isotropic mechanisms |
| Q(16) | RHO = Density of the solid phase |
| Q(17) | Q = Deviatoric stress |
| Q(18) | TEMP = Temperature |
| Q(19) | SUCTION = Suction |
| Q(20) | PC = Critical pressure |
laws/acmeg.txt · Last modified: 2020/08/25 15:46 (external edit)
