  Aims: We study the relations between stellar kinematics and chemical
abundances of a large sample of RAVE giants in search for selection criteria
needed for disentangling different Galactic stellar populations. Methods: We
select a sample of 2167 giant stars with signal-to-noise per spectral
measurements above 75 from the RAVE chemical catalogue and follow the analysis
performed by Gratton and colleagues on 150 subdwarf stars spectroscopically
observed at high-resolution. We then use a larger sample of 9131 giants (with
signal-to-noise above 60) to investigate the chemo-kinematical characteristics
of our stars by grouping them into nine subsamples with common eccentricity
($e$) and maximum distance achieved above the Galactic plane ($Z_max$).
Results: The RAVE kinematical and chemical data proved to be reliable by
reproducing the results by Gratton et al. obtained with high-resolution
spectroscopic data. Our analysis, based on the $e$-$Z_max$ plane combined with
additional orbital parameters and chemical information, provides an alternative
way of identifying different populations of stars. In addition to extracting
canonical thick- and thin-disc samples, we find a group of stars in the
Galactic plane ($Z_max<1$ kpc and 0.4 $< e < $0.6), which show homogeneous
kinematics but differ in their chemical properties. We interpret this as a
clear sign that some of these stars have experienced the effects of heating
and/or radial migration, which have modified their original orbits. The
accretion origin of such stars cannot be excluded.
