Max. Equivalent Fluid Density

[WCBS]

I am looking for the maximum equivalent fluid density of soil used in the design of poured concrete retaining walls (see Reward Wall Systems). The borings encountered SC overlying CL with N-values from 7 to 19. Is there any similarity between the equivalent fluid density and equivalent fluid pressure? Thanks for your input.

 

[RWF7437]

Equivalent Fluid Density and Equivalent Fluid Pressure are, I think, synonymous. The highest I've encountered are about 80 or 90 lb/cf. These seem pretty high for the soils you have described. For those, with a level backfill you probably have about 45 or 50 lb/cf EFD. You should, of course, calculate the Rankine or Coulomb Active earth pressure coefficient which will lead you to the correct EFD to use.

 

[Ginger]

The equivalent fluid density concept comes from the old code of practice CP2. Usually, this is taken as 5 kN/m2

 

[JYChen]

Because the equivalent fluid density or equivalent fluid pressure is another form to present the lateral earth pressure, it can vary according to the wall movement and groundwater conditions. For example, if it is a rigid wall, I will probably calculate the equivalent fluid density based on the at-rest earth pressure instead of the active earth pressure. If the retained soil is below the water table, the water pressure should probably be accounted for. If there is fill behind the wall, the earth pressure from the fill instead of the native soil should be used to get a quivalent fluid density.....

 

[dpa]

Hi RWF7437,

I printed this thread out back when it was new. I am about to send some info to a mining engineer in Canada about max pressures. In that thread, which he started, some engineers expressed the opinion that pressures never even get up to full hydrostatic. I disagree and so does at least one of my reference books. I plan to fax a copy of this thread to him too but I was wondering ,were those 80 to 90 pcf equivalents you mentioned measured or calculated. I have calculated equivalent hydrostatics as high as 81 pcf. I am looking for as much info to back up the higher pressures as possible, especially if it was gained by some kind of actual field testing. Also I am interested in finding out what kind of tests could be conducted say near the face of a retaining wall or bulkhead.

Thanks,
DPA