Ground Improvement Problems in Plaxis


 Hi all,

First of all, nice to joint this forum.

I have a project for ground improvement where the soft clay (SPT = 1) is 17 m depth.. An embankment of 4 m will be constructed on top of the original soil. The desgin load is 21.2 kPa.  I proposed DGC (Displacement Grout Cement) arranged in square pattern as an alternative method. This method require first 1m of the embankment should be comprised of sand so as to distribute the  load to the original ground and the columns.  The water is 2.8 m above the original soil.

I used axysimmetry model in PLAXIS to analyze the ultimate settlement, bearing capacity, and side friction of a single columns. In this case, I use undrained parameters for the layers.

I would like to ask questions  :

1. In the calculation stage, should I check or uncheck the checkbox "Ignore undrained behaviour"? The results are different each other if I choose to check or uncheck the box ?

2. Why the results are different each other ?

3. What considerations should be taken in determining wheter the box should be checked or or unchecked ?

Thank you

Kind regards

Soil Mechanics / Geotechnical Analysis Ground Improvement

Asked 19/06/2014 04:31, updated: 14/03/2017 14:08
Alex

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3 Answers

Votes: 1

Jasper Van der Bruggen

Hello,

The online Plaxis Knowledge Base has an entry on considerations and consequences of the “Ignore undrained behaviour” option, including for loading problems (e.g. embankments): http://kb.plaxis.com/tips-and-tricks/safety-analysis-and-undrained-behaviour
If after consulting the Knowledge Base you still have questions I refer you to the Plaxis Support: www.plaxis.com/contact/

Thank you,

Jasper


Votes: 1

MYINT Win BO

If you checked ignore undrained the program will run the drained condition considering the ground has already consolidated under current stress level.

Beaing capacity needs to be under undrained condition.

 


Votes: 1

Alex

Thank you all for your answers.