Recently i have modelled the soil pile interaction using Abaqus CEL method. The hypoplastic behavior of the soil is model using user subroutine VUMAT. The properties of the hypoplastic sand are attached. Thanks to Dr. David Mason and all other who have contributed in developing this user subroutine along with explicit interface.
i have applied an initial stress field of 0.17 MPa and the vertical length of the soil model is 9.5 meter. An initial vertical displacement of 2. meter is applied to the pile with step time of 1 sec. in in the next phase a load of 250 KN is applied with step time of 0.1 sec. The the problem is the stress on the soil around the pipe start decreasing as the pile touches the soil and then gradually reduced to zero. The vertical displacement is applied using 50 stress increments,.
The problem is the soil elements around the pile cannot withstand the load and deformed excessively. Is this issue related to my material properties or vertical length of the model is not enough to support the initial vertical consolidation. i have attached the picture of sand deformation. Waiting for the kind assistance. Thank you