About N corrected values

[JCAZ15]

Hi, In the place I am, my boss asked me to correct the SPT N values for dilatancy (dilatancia) and overburden, I am using the peck correction (0.77 log20/p) and the liao Whitman corrections, but when you are about 40 mts you get some values of 0.50 or less.

The question is: Is there any bibliography that gives a recomendation of the minimum Cn value, for example, "use a Minumun Cn value of 0.50"; if so, which is?

We are using a method to calculate skin and tip bearing capacity by means of Wysockey (1999), but I can get the original thesis, some one has it? he is from the Urbana Illinois University.

Thanks

 

[dgillette]

If you are doing this for liquefaction assessment, you should be using Idriss and Boulanger's Cn, which you may be able to find on Boulanger's web page at U of California at Davis. Liao and Whitman's is over-conservative for dense material and under-conservative for loose materials. Liao and Whitman's came from just splitting the difference between the curves for denser and for looser materials in the older work by Seed, Idriss, and others. The older work (two separate curves) fits pretty well with Idriss's recent density-dependent curves.

If you are doing something different from that, be consistent with how the empirical models were developed. I am not familiar Wysockey's work. Your best bet for that is to contact the university, especially if you can identify his or her thesis adviser.