The Barton’s characterization application allows determining the Barton’s Q (varying from 0.001 to 1000) and some strength characteristics of the rock mass: a frictional component, a cohesive component, and the static deformation modulus. Through the Q parameter, which is a function of RQD, Jn, Jw, Ja, Jr, SRF, it is possible to carry out a classification of the rock mass.
Developed in 1974 at the Norwegian Geotechnical Institute essentially for application in underground excavations, in recent years it has been extended to various fields and recently, in 2002, Barton himself proceeded with a total revision of the system.
The Q value is calculated from:
Q=(RQD/Jn)·(Jr/Ja)·(Jw/SRF)
Where the various indices are:
RQD (Rock Quality Designation), which takes into account the subdivision of the rock mass
Jn (Joint Set Number), which depends on the number of joint sets present in the rock mass
Jr (Joint Roughness Number), which depends on the roughness of the most unfavorable joint set
Ja (Joint Alteration Number), which depends on the degree of alteration of the fractures, the thickness and the nature of the infilling, and which is also determined on the most unfavorable joint set
Jw (Joint Water Number), which depends on the hydrogeological conditions
SRF (Stress Reduction Factor), which is a function of the stress state in massive rocks or tectonic disturbance.
Recently, Q has been normalized with respect to the uniaxial compressive strength of the rock, a parameter previously considered irrelevant:
Q=(RQD/Jn)·(Jr/Ja)·(Jw/SRF)·σc/100