MSE soil parameters for global stability analysis

[bosy]

What value of c and phi are appropriate for the material (compacted sand) in an MSE wall? Obviously the sand must have a phi of about 36 degrees. However, when running a global stability analysis, there must be some theoretical c, otherwise the wall cannot stand vertically. I seem to remember giving it a c of 800 psf. Another way I have seen it done is to put an extremely rigid layer at the base of the wall so that a failure circle does not pass through it. I use XSTABL for my analyses.

 

[72shortbox]

That is how I analyze walls. I make the wall mass ridged with a high fiction and cohesion to force the failure circles outside the wall. I do a seporate analysis to make sure the wall mass is stable

 

Dear guys,

I don't think you can get a material call sand with such a high cohesion. The c in sand depeds on the confining pressure of the test( CIU or CID). c normally don't used in MSE with sand as fill, even you compact it. Soils don't normally behave as you wish

Cheer.

 

[ed34]

I agree with Austgino in that the sand does not have a cohesion value. MSE walls are able to stand vertically due to the stress transfer in the system, not because of the cohesion in the material. However, I do agree with the design approach taken by bosy and basford for checking global stability. When using xstabl, I assume that the internal stability of the reinforced fill has already been checked and that only external stability is a concern. In that case, giving the reinforced fill section high strength values to force the failure outside of the reinforced block is also the way I would approach the analysis.

I also have a question regarding drainage of MSE walls. What is the typical behind wall drainage specifications in your areas? Do you just require a free-draining gravel/drainage system directly behind the wall facing or do you require it at the back of the reinforced fill section/face of cut as well?

Your experiences would be greatly appreciated.

 

[Zeccos]

When analyzing for global stability you just want to make sure that the wall is very rigid and stable. Just use very high values of the c and phi. You do not want any failure surface to cross the MSE wall anyway.

Dimitris P. Zeccos