Hemlock (Hemlock, 1999)

UCS = 0.001750M – 3043

where:

0.001750 is adimensionless constant.

3043 is in psi.

M is P-wave modulus in psi.

The Hemlock equation is derived for Cook Inlet (Alaska) unconsolidated fine to coarse-grained sandstone obtained from depths shallower than 10,000 feet (moderately low-strength rocks). M modulus is calculated from density and acoustic logs, as M = Rhob ´ V_p². Application of the Hemlock equation to rock types other than those for which it was derived generally results in a very low UCS relative to that derived by other equations.