|CREEP, PRIMARY, SECONDARY ETC.
Time dependent deformation during which the strain rate usually drops. The slope of the time strain curve generally starts decreasing. This is also known as primary creep.
The time dependent deformation during which the rate of deformation is more or less constant. In other words, the slope of the time strain curve would be of the same degree. The most interesting characteristic of constant stress tests is that steady state creep is achieved. This is a state where the rock exhibits no change of strain with time. Steady state creep occurs during the linear portion of the strain-time curve.
In tertiary creep, the strain rate again begins to fall. If the stress is tensile, the sample fails by first necking and then followed by rupture in tension.