Graded Filter Design cont.
Graded Filter Design cont.
(OP)
This is an addtional question/discussion to the original post...
The reference materials proved quite useful in the previous thread. I was wondering though, these manuals refer mainly to granualar soil. Does anyone know if the same pricipals should be applied to layering aggregate/rock materials?
For example I have a native soil base, then a con sand layer, then a layer of no. 57 aggregate, and I want to put a layer of larger drain rock on top of the no. 57...do I have to run the same calculations I ran for the granualar soil interfaces on the rock/aggregate interface?
I don't know if anyone actually will know the answer to that one, but any input would be appreciated? Thanks.
The reference materials proved quite useful in the previous thread. I was wondering though, these manuals refer mainly to granualar soil. Does anyone know if the same pricipals should be applied to layering aggregate/rock materials?
For example I have a native soil base, then a con sand layer, then a layer of no. 57 aggregate, and I want to put a layer of larger drain rock on top of the no. 57...do I have to run the same calculations I ran for the granualar soil interfaces on the rock/aggregate interface?
I don't know if anyone actually will know the answer to that one, but any input would be appreciated? Thanks.





RE: Graded Filter Design cont.
This is one of those "engineering judgement" situations. It will depend, I think, on which way the hydraulic gradient runs. You definitely don't want sand boiling up into openwork gravel. But if the hydraulic flow will be downward, then I would tend to think that placing open gravel on top of sand shouldn't be as big a deal. Potential for flow to run both directions indicates that care must be taken to look at both flow regimes. However, it's been quite some time since I worked on earthfill dams, so I will happily listen to any dissenting opinion.
Jeff
Jeffrey T. Donville, PE
TTL Associates, Inc.
www.ttlassoc.com
RE: Graded Filter Design cont.