Dear All,
I am using ISA+HP model in my research and I have encountered some problem when looking into cyclic triaxial test for single element.
The target model was selected from Professor Wichtmann lab test ( TCUI11). This sample is a cyclic test for Karlsruhe fine sand. Also, for sand modelling the ISA+HP model was used (Fuentes, W., Wichtmann, T., Gil, M., & Lascarro, C. (2020). ISA-Hypoplasticity accounting for cyclic mobility effects for liquefaction analysis. Acta Geotechnica, 15(6), 1513-1531.).
Confining pressure is equal 200KPa and deviatoric stress was considered base on sinusoidal loading with Amp=40KPa (100 cycle).
The result of E22 is not desirable and in the curve E22 versus q no loop is observed.
Could you please tell me what is the main wrong in this simulation?

qdeviatoric-stress-4.JPG ISA-3.JPG E22Vertical-Stress-1.JPG E22-q-2.JPG 2D-0.JPG

  1. Jose Duque
    Jose Duque 3 years ago

    Dear Mehdi,

    I was checking the parameters that you reported and I noticed two issues:

    1) The mechanical constant 7 is “eio”. You are using 0.842 which is below “eco”, which is not correct. Professor Fuentes reported in his calibration for Karlsruhe fine sand ei0=1.212

    2) I do not know which implementation of the HP+ISA model are you using, but usually in the umats of professor Fuentes the friction angle is input in radians, please verify that

    One last comment, in order to reproduce the cyclic test results reported in that paper, you should simulate the preloading history of the test (isotropic compression) or initialize tensors h and c as isotropically fully mobilized

    Kind regards,

    • Mehdi Joneidi Author
      Mehdi Joneidi 3 years ago

      Dear Jose,
      Thank you for your comment.
      Yes, the value of maximum void ratio at p=0 was incorrect and modified to ei0=1.212 but the model is so sensitive to phic when the phic=0.56 after few cycles the verical strain dramatically increase while this condition don’t observe in phic=32.6!!

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