GMI-Teikoku-Nphi

UCS = 2900e(–5.3 ´ Nphi)

where:

2900 is in psi.

5.3 is unitless.

Nphi is neutron log value expressed as a fraction.

This equation is derived from the correlation of triaxial test results on eight volcanic core samples with neutron log in a well in northwest Japan. The core density ranges between 2.4 and 2.6 g/cm³. The reported UCS ranges between 8,000 and 18,500 psi.