Table 3.

Conversion factors from the literature to determine the equivalent UCS by means of PL index

ReferenceCorrelation coefficient
Anonymous (1972)16
Broch & Franklin (1972)24
Bieniawski (1975)25
Dearman & Irfan (1978)25
Al Jassar & Hawkins (1979)10–29
Lumb (1983)10–24
Franklin (1985)25
Irfan & Powell (1985)12.5–25
Hawkins & Olver (1986)10–29
Norbury (1986)12–35
Leung & Radhakrishnan (1990)6.12
Ghosh & Srivastava (1991)16
Rusnak & Mark (2000)21.9
Chau & Wong (1996)15.3–37.8
Del Gaudio (2012)10–48