Hi Roozbeh,

I have found ADONIS very useful (thank you) and I have tried to use it to model active and passive pressures on a rigid wall.

This is an attempt to emulate Program 6.5, pp.265-271 in Smith, Griffiths & Margetts book [1]. This type of problem
has also been investigated by Krabbenhoft (2018) and Nguyen, T. & Shiau (2023).

The model is a 1.0m high wall, soil unit weight 20 kN/m^3, angle of friction=30 deg, cohesion=0, dilation angle = 30 deg, wall friction = 0 deg, wall cohesion=0.

I assume that ADONIS is able to model this type of problem? So far the results I have obtained are promising, although the load for active seismic case seems significantly higher than those reported by M-O and Krabbenhoft.

But I'm not sure I am using the best model, or the best way of calculating the load against the wall. Also Smith et. al. did not use a wall as such, but simply displaced the nodes where the virtual wall was.   Suggestions for improvements most welcome.


References
----------

1. Smith, I. M., Griffiths, D. V. & Margetts, L.
   Programming the Finite Element Method. (John Wiley & Sons Ltd, 2014).

2. Krabbenhoft, K.
   Static and seismic earth pressure coefficients for vertical walls with horizontal backfill.
   Soil Dynamics and Earthquake Engineering 104, 403?407 (2018).

3. Nguyen, T. & Shiau, J.
   Revisiting Active and Passive Earth Pressure Problems using Three Stability Factors.
   Computers and Geotechnics 163, 105759 (2023).

Hi Peter,

Your script is quite impressive, and I'm glad to hear you're finding ADONIS useful! Regarding your question, I'm not familiar with the specific example from the book. However, if you apply a similar approach, you should be able to achieve comparable results (though they might not be exactly the same). If you can share the example here, it would help clarify things further.

-Roozbeh

Hi Roozbeh,

I have updated my script to include initiliasing the stresses, as per program 6.5, where at-rest K0=1.0.

I also misunderstood the meaning of initial("movexdir", val, ...): I had though it was setting an absolute displacement, but I think it adds an incremental displacement. The results now look better.

I have also attached a Python script  "earth_pressure_plot_sxx.py"  that will process the generated data .dat files to create:
(a) a plot of wall force versus displacment
(b) stress profile for each iteration

NB: the plot script currently assumes the wall height is 1.0, so annotations in the force vs displacement plot will
be incorrect if a different height is used.

The Python script uses matplotlib to generate the plots.  After generating the output .dat and .vtk files by running the script in ADONIS, create a new directory, and cut and paste all the generated .dat and .vtk files into this new directory. Then to generate the plots run: 

  python earth_pressure_plot_sxx.py <new_dir_name>

In the script "earth_pressure_on_rigid_wall.ajs" the primary variables to change are:
- state ('active', or 'passive')
- k_h  (0.0 for static, -ve for seismic to the left)
- initialize_stress (true or false)
- K0  (default is 1.0)


Peter

Peter, this is fantastic. I am sure this example proves helpful to other users as well.

Hi Roozbeh,

I forgot to mention that the Python script "earth_pressure_plot_sxx.py" was not run from within ADONIS, but will (usually) require a 64-bit version of Python, as there is no standard pre-compiled 32-bit release of the package "matplotlib". While it is possible to compile a 32-bit version of "matplotlib" this may require a reasonable amount of effort to build.

I have obseved a curious oscillation in the sxx profile. At the first iteration at disp_x=0, the stress profile is almost linear, but oscillations occur with increasing displacement. Attached are some sxx profiles for the active case. I increased the stiffness of the wall, but still observed the oscillation. The same oscillation is observed if the number of wall elements is increased to 20.

Peter

Hi Roozbeh,
Attached are some plots comparing ADONIS results with those from program 6.5 of Smith, Griffiths & Margetts (2014).
Peter