Rzhewski-Phi (Rzhewski and Nowick, 1978)
UCS = A ´ (1 – BΦ)2
Default constants: A = 40,000; B = 3 (B between 2 and 5).
A is in psi.
B is a non-dimensional constant.
This equation is from a Russian reference and no information about the samples is currently available. The equation is similar to the Vernik formula but with different constants. The empirical constant A refers to UCS in a zero porosity limestone and the empirical constant B may be adjusted based on the overall porosity (smaller B value for higher porosity samples).