Hello to everyone! I´m modelling a simple stratfication composed by 3 layers. The top layer is silt, the midle one is sand and in the bottom is bedrock. In the borehole section I defined the water level to be below the bedrock, but i´m getting excess pore pressure in my sand layer. How can I solve it?
The main porpouse is to model the liquefaction suscetability of the sand layer, and if the water level is below the bedrock layer I should not have excess pore pressure in my sand layer right?
Please help me because in less than a month I have to deliever my masters thesis. Thanks in advance for the help.
Dear Rui,
The phreatic level is the level for which pore pressures are zero: below the phreatic there are pore pressures and above the phreatic line there are pore water suctions as the soil is unsaturated - but not necessarily dry. Depending on whether you have defined your material above the phreatic level as drained or undrained in combination with a Plastic, Dynamics or Safety phase or whether you're performing a Consolidation, Dynamics with consolidation or Fully-coupled flow deformation analysis excess pore pressures may form in the unsaturated zone.In principle if you would define your material as drained and you perform a Plastic, Dynamics or Safety analysis, no excess pore pressures will develop. However, if you perform a Consolidation, Fully-coupled or Dynamics with consolidation analysis the unsaturated soil effect is taken into account and excess pore pressures based on the the degree of saturation and soil permeability will develop.
With kind regards,
Dennis Waterman
Dear Dennis,
Thank you for your help!