DCP to SPT II

[MRM]

I saw that Moe had a post (now a closed thread) about DCP to SPT correlations and related items. I thought I'd share a recent paper of mine that considers some things along these lines (SPT to Sowers DCP correlations, various somewhat interesting ways in which the DCP might be used, results of some case studies along with some test pit tests for check into the correlations further, etc.).

My apologies if I've already provided this before, but have since forgotten in all the craziness of life...

The soil featured is a uniform Michigan beach sand. For that type of soil, at least, I'm perfectly fine with taking the Sowers DCP to SPT relationship as an approximate 1:1. Lots of DCPs out there, but I've always been partial to the Sowers DCP for my work. And even if you have a different style, what I've got here may still be able to provide some general insight about trends that you might expect for relative density and SPT-to-DCP correlations...

This little paper was a fun one to put together and present!

I'm currently doing some work in a similar type of way with some of the more well-graded sands that sand and gravel pits generally provide as fill material for construction in eastern Washington. Very interesting, yet not surprisingly, the DCP to relative density correlation for these eastern Washington sands is quite different than the uniform sands!

All the best,
Mark

 

[oldestguy]

The paper deals with uniform sands, at least some of which are similar to standard Ottawa sand as used for various laboratory tests. There is a paper by B.K. Hough "Compressibility as the Basis for Soil Bearing Value", August 1959, ASCE SM 4, 2135. He also has some of this info in his Text: "Basic Soil Mechanics". In his charts he shows the difference in support capability, on the basis of potential for footing settlement of some typical soils, varying from uniform sands to clays. Specifically he shows that for the same N value of SPT the uniform sands have better bearing capability than well graded sands. In my experience that is true. Some discussion contributors to his paper verify his chart is quite valid for sands. I liken the differences to the difference in supporting (compression) capability between a bucket of marbles to that of well grade gravel.

In summary, I'd expect that maybe the DCP might work the same as STP for these different sands.