I am trying to use SANISAND as the constitutive model of soil, and use ABAQUS software to simulate pile-soil interaction. First step is “Geostatic”, the second step is “Static, General”. The first picture is the model parameters of SANSAND, and the second picture is the contour map of state variable 29 (sdv29).
As you can see, the red part in the second figure indicates that the excess pore water pressure U of the soil is negative, because UMAT sets the state variable 29 – excess pore water pressure U equal to the volume strain of the soil element multiplied by the volume modulus of water, that is, the volumetric strain of the soil element is positive(dilatancy). Is this normal? I have changed the initial void ratio of the soil several times, but the value of state variable 29 of the soil element near the pile is not negative. Can anyone explain this situation?