Stress Sign Conventions

There are multiple commonly-used methods of referring to the three principal stress values. Consequently, this is an area that is particularly subject to engendering confusion. It is important to remember at all times that in Itasca codes, positive stresses indicate tension; negative stresses indicate compression.

The table below summarizes some terminologies used to denote stress and how they relate to one another.

Table 1: Principal Stress Conventions

in	Negative (-)	Positive (+)	Intermediate ( )
Itasca codes (\(σ_{1}\) ≤ \(σ_{2}\) ≤ \(σ_{3}\) by default )	minimum	maximum	intermediate
general usage in geomechanics	major	minor	intermediate
symbols	\(σ_{1}\)	\(σ_{3}\)	\(σ_{2}\)