Hi Prof. David,
I have obtained these results in that attached picture using Triax and got confused when seeing that an isotopically normally consolidated sample does not follow a trend that looks similar to the traditional Roscoe Surface. Have I done something wrong or this is what is expected from your hypoplastic model?
Thank you,
Hashmi
Undrained Tests with Basic Clay Hypoplasticity
Related Articles

Errors of sand hypoplastic model with Abaqus Vumat
Kunpeng WangConstitutive Modelling9 Views 351
Dear all, Recently, I have been working on the simulation of a pilesoil interaction with CEL method in Abaqus/Explicit. I simulate the sand with the Sand Hypoplasticity Model provided by […] 
testing an User Defined Soil Model in plaxis
MIGUEL VALENCIA GALINDOConstitutive Modelling1 Views 509
Hi everyone I am writing a code for a model in the UDSM format for Plaxis. I already have the “*.dll” files, but when I run the soil test I […] 
Cyclic simple shear test simulation with hypoplasticity
Piotr KowalczykConstitutive Modelling2 Views 575
Dear All, I am using sand hypoplastic model in my research and I have encountered some problem when looking into cyclic simple shear test in the range of small strains. […] 
Calibration of Hypoplastic material model parameters
Amine AboufirassConstitutive Modelling6 Views 622
I would like to derive material parameters based for a simulation which will implement the hypoplastic material model based on the following information: • Heavily overconsolidated • Very dense, fine […] 
Nonlocal regularization: Need VUMAT of MohrCoulomb model in abaqus
Kunal Sanjay PardikarConstitutive Modelling1 Views 508
Dear Community, I want to include a nonlocal regularization technique in the builtin MohrCoulomb model of abaqus to capture the strainlocalization effects. I am trying to find the original VUMAT […] 
SANICLAYB (2018) how to calculate Dep
Steve XuConstitutive Modelling0 Views 378
Dear fellows, I have been working on coding SANICLAYB model (2018) . Now I have one question in terms of this model. But I am stuck now. I have two […] 
Calibration problem
Abdulaziz AbdelkadrConstitutive Modelling2 Views 329
Dear Prof. David Mašín I am posting the queries I have emailed you as per your advice to post it here. During calibration for the basic hypoplasticity parameters using the […] 
CEL analysis using hypo plasticity Vumat
abd ElfattahConstitutive Modelling8 Views 895
Greetings i used interface Vumat with Umat for simulating CEL problem, after 50% of analysis, i got the error as “Excessive incremental rotation of the elements in element set ” […]
Who is Online
No one is online right now
Search SoilModels Website
Recent posts
 Two postdoctoral positions in computational mechanics in Ben Gurion university and Ariel university, Israel, are available immediately 28.2.2021
 K0 determination Reloading using HP clay model 22.2.2021
 Seismic Liquifaction 11.2.2021
 Modelling cyclic loads in Tochnog 11.2.2021
 Soft soil model vs Soft soil creep model 8.2.2021
 Boundary value problems for granular materials subjected to earthquake loading 8.2.2021
 Guidance for a newbie 6.2.2021
 Modelling Ratedependent behaviour of clay [Urgent] 1.2.2021
 Postdoctoral Fellowship in computational geomechanics 27.1.2021
 USDM – Creep SCLAY1S 25.1.2021
 Hardening Soil Model in Abaqus 25.1.2021
 Effects of water content in sand in hypoplastic strength parameters 25.1.2021
Recent Comments
 Mehdi Joneidi on A problem of convergence from using Hypoplastic model in Abaqus
 Mehdi Joneidi on Boundary value problems for granular materials subjected to earthquake loading
 Mehdi Joneidi on Kadlíček, T. and Mašín, D. (2020). The strength reduction method in clay hypoplasticity. Computers and Geotechnics (in print)
 David Mašín on Kadlíček, T. and Mašín, D. (2020). The strength reduction method in clay hypoplasticity. Computers and Geotechnics (in print)
 Mehdi Joneidi on Kadlíček, T. and Mašín, D. (2020). The strength reduction method in clay hypoplasticity. Computers and Geotechnics (in print)
 Micha Van der Sloot on PM4Sand for Plaxis Download
 Eduardo Muguet on PM4Sand for Plaxis Download
 Sudipta Bhowmick on Subroutine of SANISAND model
 Sudipta Bhowmick on SANISAND (Dafalias and Manzari, 2004)
 Osama Dar on Guidance for a newbie
 Arie Koot on Seismic Liquifaction
 Emrecan Güven on Guidance for a newbie
 Osama Dar on Guidance for a newbie
 Gertraud Medicus on Guidance for a newbie
 Juan Tello on Clay hypoplasticity with strength reduction (umat and Plaxis dll).
 Juan Tello on UMAT Implementation of Sand Hypoplasticity by UIBK
 Micha Van der Sloot on PLAXIS
 Micha Van der Sloot on USDM – Creep SCLAY1S
Dear Hashmi, this is correct response of the model. Actually, the observed shape of stress path is due to response envelopes being translated elipses in the stress space. The normally consolidated sample response can be corrected by either using intergranular strain concept, or by socalled Ddependent L approach. It is discussed thoroughly in this reference: Mašín, D. and Herle, I. (2007). Improvement of a hypoplastic model to predict clay behaviour under undrained conditions. Acta Geotechnica 2, No. 4, 261268. Regards David
ok, thank you David.
Can you please provide a clarification on the following:
In triax program, the following are the inputs when using hypo_clay with istrain:
fi cr, lambda, kappa, N, r, R, mr, mt, betar, chi, e0
however, when referring to your notes, it says that for hypo_clay mR is replaced by Ag and ng while mT is supplemented by mrat instead. Therefore, how can i make triax recognise these input parameters: Ag, ng and mrat?
Correct, this is because hypo_clay is 2005 version of clay model. To use the most recent clay version, use hypo_clay_anisot and set anisotropy factor alpha_G = 1. Regards David
ok thank you. is there an updated pdf manual that includes the newer versions of hypo_clay models in triax that came after 2005?
I am currently using hypoplasti_clay_anisot_istrain, can you please confirm that the parameter nu is poisson’s ratio?
Hi David,
Can you please clarify the following parameters in Triax:
hypoplasti_clay_anisot_istrain: fi cr, lambda, kappa, N, nu, alpha, R, betar, chi, G0, n, mtrat, inic. his. var.: e0, istrain, pt
1. what is G0? confused that it could mean Ag or is it just initial shear stiffness?
2. is the n the same as ng?
3. what to insert for istrain and pt after e0? (i initially left them blank)
Thanks!
Hi Hashmi, G0=Ag, n=ng,
for istrain you should put all 9 components of complete intergranular strain tensor (rowbyrow) with x being vertical coordinate, that is [isxx, isxy, isxz, isyx, isyy…]. For initial state, you probably want to set nine zeros.
for element test simulations, you will probably use pt=0, as you will not need to cope with nearzero stress problems occuring often in FE simulations. pt is arbitrary (you can leave it blank), but at least nine zeros for istrain (or your values if you know what you are doing) are important.