u/No_Preparation8438

Hi everyone,
I’m currently working on a project where we performed Dynamic Cone Penetrometer (DCP) tests and obtained DCPI values (mm/blow). I would like to estimate equivalent SPT N-values from the DCPI results.
I understand that:

1. DCPI ↔ CBR correlations are fairly well established in pavement/subgrade evaluation.
2. Direct DCPI ↔ SPT N correlations are less common and appear to be soil-specific.
3. Some researchers suggest site-specific regression if paired DCP and SPT data are available.

My questions are:

1. Are there any well-cited studies or published correlations directly relating DCPI to SPT N?
2. Is it more defensible to go DCPI → CBR → SPT N using existing empirical relationships?
3. From a practical standpoint, would you recommend developing a site-specific correlation instead of relying on published equations?

I’m mainly looking for a defensible approach for reporting purposes (preliminary evaluation, not final foundation design).
Any references, papers, or field experience would be greatly appreciated.
Thanks in advance!