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Mechanical - Mechanical constitutive model

*Material, ... 
... 
*Mechanical = <mechanical model> 
*<parameter 1>, ... , <parameter n> 
...

Set this parameter equal to the mechanical model to be used for the calculation of stresses. The subsequent lines <parameter 1>, ... , <parameter n> depend on the model chosen. This parameter is mandatory. The different "mechanical" models available in numgeo are summarised in the table below and described in the subsections accessible through the links in the table or the navigation bar on the left.

Model Section
Linear Elasticity Linear elastic model
Matsuoka Nakai Linear elastic - perfectly plastic model with Matsuoka-Nakai yield and failure criterion
Modified Cam Clay Generalized Modified Cam-Clay (MCC) model with control over the shape of the yield surface and the stress ratio at critical state
Mohr-Coulomb Linear elastic - perfectly plastic model with Mohr-Coulomb yield and failure criterion available in two different implementations
Advanced constitutive models
AVHP Anisotropic Visco-Hypoplasticity (AVHP) as proposed by Niemunis & Grandas (2009)1
AVISA Anisotropic Viscous ISA model after Tafili & Triantafyllidis (2020)2
BC-HYPO-IGS-SF Bio-Cemented Hypoplasticity + Intergranular Strain + Semi-Fluidized State and Fabric Change Effects
Extended Bounding Surface Extended bounding surface model
Hardening soil (MN) Hardening soil model with Matsuoka–Nakai (MN) failure surface
Hypo-Clay Hypoplastic constitutive model for clays proposed by Masin (2005)3
Hypoplasticity + Generalized Intergranular Strain Hypoplastic model for sand according to von Wollfersdorff (1996)4 with generalized intergranular strain anisotropy extension (Mugele et al. (2024)5)
Hypoplasticity + Intergranular Strain Hypoplastic model for sand according to von Wollfersdorff (1996)4 with intergranular strain extension (Niemunis and Herle, 1997)6
Hypoplasticity + Intergranular Strain Anisotropy Hypoplastic model for sand according to von Wollfersdorff (1996)4 with intergranular strain anisotropy extension (Fuentes et al., 2020)7
Hypoplasticity + ISA-SF Hypoplastic model for sand according to von Wollfersdorff (1996)4 with intergranular strain anisotropy (ISA) and semi-fluidized state (SF) extension (Tafili et al., 2024)8
Sanisand Critical state compatible bounding surface plasticity model according to Dafalias & Manzari (2004)9 available in two different implementations
Sanisand-F Extension of the Sanisand model9 to incorporate effects of fabric by Petalas et al (2019)10
Sanisand-MSf Extension of the Sanisand model9 to incorporate effects of memory surface and semi-fluidized states according to Yang et al. (2022)11
High-cycle accumulation models
HCA for Clay High-Cycle Accumulation (HCA) model for clay12\(^,\)13. The current implementation allows coupling with the following models: AVISA, AVHP, MCC
HCA for Sand High-Cycle Accumulation (HCA) model for sand as proposed by Niemunis et al. (2005)14. The current implementation allows coupling with the following models: Hypo-IGS, Hypo-ISA, Sanisand, Linear Elasticity

References

  1. A Niemunis, C E Grandas-Tavera, and L F Prada-Sarmiento. Anisotropic visco-hypoplasticity. Acta Geotechnica, pages 293–314, 2009. ↩

  2. M Tafili and T Triantafyllidis. AVISA: Anisotropic Visco ISA model and its performance at cyclic loading. Acta Geotechnica, 15:2395–2413, 2020. ↩

  3. D. Masin. A hypoplastic constitutive model for clays. International Journal for Numerical and Analytical Methods in Geomechanics, 29(4):311–336, 2005 2005. doi:10.1002/nag.416. ↩

  4. P.-A. Wolffersdorff. A hypoplastic relation for granular materials with a predefined limit state surface. Mechanics of Cohesive-frictional Materials, 1(3):251–271, 1996. doi:10.1002/(SICI)1099-1484(199607)1:3<251::AID-CFM13>3.0.CO;2-3. ↩↩↩↩

  5. L. Mugele, H.H. Stutz, and D. Mašín. Generalized intergranular strain concept and its application to hypoplastic models. Computers and Geotechnics, 173:106480, 2024-09. doi:10.1016/j.compgeo.2024.106480. ↩

  6. A. Niemunis and I. Herle. Hypoplastic model for cohesionless soils with elastic strain range. Mechanics of Cohesive-frictional Materials, 2(4):279–299, 1997. doi:10.1002/(SICI)1099-1484(199710)2:4<279::AID-CFM29>3.0.CO;2-8. ↩

  7. William Fuentes, Torsten Wichtmann, Melany Gil, and Carlos Lascarro. ISA-Hypoplasticity accounting for cyclic mobility effects for liquefaction analysis. Acta Geotechnica, 15(6):1513–1531, 2016. URL: http://link.springer.com/10.1007/s11440-019-00846-2, doi:10.1007/s11440-019-00846-2. ↩

  8. Merita Tafili, Jose Duque, David Mašín, and Torsten Wichtmann. A hypoplastic model for pre-and post-liquefaction analysis of sands. Computers and Geotechnics, 171:106314, 2024. ↩

  9. Yannis F. Dafalias and Majid T. Manzari. Simple plasticity sand model accounting for fabric change effects. Journal of Engineering mechanics, 130(6):622–634, 2004. ↩↩↩

  10. Alexandros L. Petalas, Yannis F. Dafalias, and Achilleas G. Papadimitriou. SANISAND-F: Sand constitutive model with evolving fabric anisotropy. International Journal of Solids and Structures, 188–189:12–31, 04 2020. doi:10.1016/j.ijsolstr.2019.09.005. ↩

  11. Ming Yang, Mahdi Taiebat, and Yannis F. Dafalias. SANISAND-MSf: a sand plasticity model with memory surface and semifluidised state. Géotechnique, 72(3):227–246, 03 2022. doi:10.1680/jgeot.19.P.363. ↩

  12. T Wichtmann. Soil Behaviour Under Cyclic Loading: Experimental Observations, Constitutive Description and Applications. Habilitation, Institute of Soil Mechanics and Rock Mechanics, Karlsruhe Institute of Technology, Issue No. 181, 2016. ↩

  13. Patrick Staubach, Jan Machaček, Merita Tafili, and Torsten Wichtmann. A high-cycle accumulation model for clay and its application to monopile foundations. Acta Geotechnica, 17(3):677–698, mar 2022. doi:10.1007/s11440-021-01446-9. ↩

  14. A Niemunis, T Wichtmann, and T Triantafyllidis. A high-cycle accumulation model for sand. Computers and Geotechnics, 32(4):245–263, 2005. doi:https://doi.org/10.1016/j.compgeo.2005.03.002. ↩