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Excavation and Backfilling

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fo2sh

Civil/Environmental
Aug 18, 2008
5
HI everyone,
I am new user of ABAQUS and I would like to discuss my model simulation with other users.
I am trying to simulate the soil - pipe interaction where the pipe is laid in a trench.
The sequence of the construction process is the following:
1- excavating the trench
2- applying the pipe
3- Backfilling.

Based on my readings for other threads posted I knew the best way to model this problem is to get use of the *ELCOPY command where I create elements on the existing elements. Then I Assign each material properties to each element set separately. Example the existing element set will be assigned the original soil properties and the copied element set will be assigned the backfill material properties.

The model steps are the following:
1-Static step Using MODEL CHANGE, TYPE=ELEMENT, REMOVE
in this step I remove all element sets that I copied
2-Geostatic Step
3- Static step Using MODEL CHANGE, TYPE=ELEMENT, REMOVE
in this step I deactivate each element set one by one that represents the trench elements to be excavated.
4-Static step USING MODEL CHANGE, TYPE=ELEMET, ADD=STRAIN FREE to activate the backfilling elements assigned the backfill material properties.


Following the above procedure resulted in weired results especially when I checked in the visualization module, I observed when I used the probing values techniques that soem of the elements are not present in certain region although in these regions either the original properties or the backfilling properties should be available.

The second unexpected observation is that the original elements sets from which the elements were copied are no longer appearing and only the ID number of the copied elements that is written in the probe values table even in the step where the copied elements should be deactivated.

Any help on how assign material change properties will be greatly appreciated.
Thanks
Sherif
 
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