Additional information on Pore pressure distribution and fixities

[ryancwl95]

Hello,

I am currently modeling a 1m thick semi-circular slice of soil within a larger soil body in transient gravity analysis at long time steps. I have set a 'no flow condition' (pore pressure degree of freedom = 0) at the top and bottom z-plane boundary nodes and along the Y-axis at the line of symmetry. At the radial boundary nodes, I am 'allowing for flow' (pore pressure degree of freedom = 1).

The obtained pressure profile is shown below:

Screenshot 2023-12-04 120247.png (118.36 KiB) Viewed 4199 times

The pressure profile around the top and bottom is -4.9 kPa to 4.9 kPa, respectively, resulting in a logical difference of 9.81 kPa for a 1m thick soil. I am curious about how the starting value of -4.9 kPa is determined.

I am also wondering about the creation of the pore pressure profile and why the pressure at the midpoint (roughly) of the slice is 0 kPa. Additionally, how is the 0 kPa reference line determined when calculating pore pressure?

When I set the outer radial boundary nodes with pore pressure degree of freedom = 0, the profile becomes:

Screenshot 2023-12-04 122423.png (90.93 KiB) Viewed 4199 times

Here, the pore pressure profile ranges from about 16.2 to 6.36 with a rough difference of 9.81 kPa. In this case, how is the starting value of 6.36 kPa at the top of the slice determined? Is there a reference line where the pore pressure profile is created/calculated?

Thank you for your assistance!

[STKO Team]

Can you share your model?