Opinions requested for use or misuse of "corrected" SPT values.
Opinions requested for use or misuse of "corrected" SPT values.
(OP)
I've been reviewing some reports in the last few years with SPT values on the logs given as "corrected". With many older tables out there based on past experience, I question anyone making any changes to the SPT values coming out from this crude test in the field. I view them as wishful thinking. Your comments?





RE: Opinions requested for use or misuse of "corrected" SPT values.
RE: Opinions requested for use or misuse of "corrected" SPT values.
RE: Opinions requested for use or misuse of "corrected" SPT values.
RE: Opinions requested for use or misuse of "corrected" SPT values.
I'll add one more caveat....Schmertman's work was done completely in coastal plains soils, so that limits its applicability.
RE: Opinions requested for use or misuse of "corrected" SPT values.
I abhor the geotech report that makes these correction(s) on the Drill Log, with NO description of what has been considered. I desire (& have reported) the basic field values, with information on the Logs and Legend describing the test & methods. The body of the report should deal with the corrections.
RE: Opinions requested for use or misuse of "corrected" SPT values.
N1_60 = N * Ce * Cn * Cb * Cs * Cr* Cbf
Some of them are 1. Ce: Energy correction factor. Cn: Overburden correction factor (we use it only for granular materials.) Cb: Drilling diameter orrection Cs: Tube type correction Cr: Rod length correction Cbf: Impact rate correction.
In order to use correlations, of course, we check for what type of SPT value that they have been used. But before 1970s energy ratio was not defined. So, correlations before that date, like Terzaghi Peck and Thornburn was based on approximately 55% energy ratio.