Pavement Deflection and Rainfall Balance.

Systematic monthly measurements of the deflexion of sections of pavements, mostly of the traditional type, were begun in 1977 in the six Regional Laboratories which constitute the base of overlay operations. These measurements were accompanied by the calculation of the rainfall balance affecting the ground, on the basis of data gathered by the nearest meteorological station, as is done for agricultural purposes. The object of the study was to observe seasonal variations of deflexion and compare them with seasonal variations of the rainfall balance. Examination of the numerous results gathered indeed reveals an analogy in the variation of these two factors, but with a variable shift between the curves representing them. It seems that this shift, and also the more or less 'typed' nature of the curves of evolution of deflexion, depends among other things on the geotechnic and hydraulic characteristics of the site under observation. Consideration of meteorological factors alone would therefore seem to be insufficient to predict the way the deflexion varies.