Slurry Modulus for Pipe Bedding

[moe333]

Hi all,

I am considering recommending 2,000 psi slurry (lean concrete) to bed a 96" steel pipe. Bedding 10" below pipe and up to springline. I typically recommend E' of 1,500 psi for crushed rock, and think I could go higher with sluury but not too sure about it. Anyone have any experience on what a reasonable E' would be for slurry?

Thanks

 

[moe333]

Correction to my original post; 2,000 psi concrete would not be considered slurry. Any thoughts on what E' to use for a true sand-cement, say 2 sack slurry with 500 psi strength.

 

[Ron]

CLSM would have a modulus of around 500ksi. Soil-cement,compacted would have a modulus of around 250 to 300 ksi. A slurry with an unconfined compressive strength of around 500 psi should have a modulus in the 300 to 400 ksi range.

 

[moe333]

The Bureau of Rec. has tables showing E' up to about 3,000 psi for well compacted SW. But I think it should be a function of the pipe depth, trench width, adjacent soil, depth of backfill as well. Anyone have a good reference that accounts for some of these factors?

 

[Ron]

moe333...are you sure on that one? Seems awfully low. We can get 10ksi out of unstable sand. Graded aggregate base would be in the 40 to 60 ksi range.

 

[moe333]

Ron, yes..USBR E' values for buried pipelines are 3,000 psi for slightly or well compacted crushed rock or well compacted SW/SP. Someone told me AASHTO may have tables that take into account the factors I discussed above. I was trying to see if anyone has values for something like a 2 sack sand cement slurry.

 

[Ron]

A "2 sack" sand-cement slurry is much like CLSM. The modulus would be in the 300 to 500 ksi range.