Pore pressures of a slope

[javykuan]

Hi all, I have been using Opensees for a while. May I ask some questions I am confused here?

1. Is that ok if I use BrickUP elements and PressureDependMutiYield material to conduct a static analysis of a slope?
2. For all of the samples they keep telling us that the velocity of dof 4 is pore pressure. How about the displacement of dof 4? As far as I know, I think the displacement of dof 4 should be the nodal pore pressure in static analysis?
3. Can I apply negative pore pressures to a node? Is that valid?

Can anyone help me with these questions? Many thanks!

[zanakarimi]

it's u-p element type not U-p-u. You cannot measure the pore fluid displacement

[javykuan]

zanakarimi wrote:
> it's u-p element type not U-p-u. You cannot measure the pore fluid
> displacement

Do you mean the displacement of dof 4 is meaningless?

[jinlu]

Yes, it's OK to use BrickUP elements and PressureDependMutiYield for static analysis. Regarding the pore water pressure, BrickUP element (and other U-P elements) uses the velocity of the last dof (i.e., dof 4 for 3D element BrickUP, or dof 3 for 2D element QuadUP) to temporarily store the pore water pressure for the recorder. I'm not sure if you can apply pore pressure to a node.
-Jinchi Lu

[fmk]

if you constrain the dof that corresponds to the pore water pressure to have some values during the analysis the elements will see these as the pore water pressure. so yes you could. think of it like imposing the displacements at the nodes (all we are doing is setting the displacements, the elements see that their nodes have moved and respond accordingly in their force and tangent responses .. the elements don't know that these are imposed displacements or coming from he solution algorithm).

[javykuan]

Thank you all very much! So to make a conclusion, if I need to assign pore pressures, I can just constrain the velocity of the corresponding dof to some values? No need to constrain acceleration, vel and disp at the same time?