OPTIMIZATION OF THE THICKNESS OF THE SUB-BASE LAYERS OF FLEXIBLE PAVEMENTS BASED ON LATERITIC GRAVEL OF AVLAMÈ IMPROVED WITH GRANITE CRUSHED STONE

Abstract

The exploitation of raw or improved lateritic gravel in road construction is of major interest. 
Such is the case of the lateritic gravel of Avlamè improved with granite crushed of Dan 0/31.5 
usable in road construction in Benin. In this perspective, the present study is initiated to 
investigate the influence of elastic (E=5CBR) and secant moduli in the determination of 
pavement base layer thicknesses. A comparative study was carried out by considering the elastic 
and secant moduli for the design of several pavement variants using the Alizé software of LCPC- 
SETRA. The results obtained show that the use of the secant modulus for the design allows a 
reduction in the thickness of the base course of 20% and 13.33% respectively for the variants V1 
and V2. As for the variants V3 and V4, no reduction is observed. Moreover, the use of the secant 
modulus for the design of the subgrade allows a reduction of 25% in the thickness of each of 
these variants compared to the use of the elastic modulus. Also, the secant modulus allows to 
reduce the thickness of the base course by 16.67% and 13.33% respectively for the variants V5 
and V6, and by 23.08% for the variants V7 and V8 compared to the use of the elastic modulus 
(5CBR). As for the design of the subbase layers, the use of the secant modulus allows to reduce 
the thickness of the subbase layers by 13.33 %, whatever the variant (V5 to V8), compared to the 
use of the elastic modulus. These results show that the thickness of the pavement structure 
decreases with increasing moduli (E=5CBR and E50).