Correlation Between Resilient Modulus and Permanent Deformation During a Large Scale Model Experiment of Unbound Base Course

Unbound base course performance is highly dependent to resilient modulus and permanent deformation of unbound layers. Plastic strains are affected by the number of traffic loading. A Large Scale Model Experiment (LSME) test was conducted on unbound granular materials for 10,000 load repetitions and different thicknesses to determine the relationship between resilient modulus and plastic deformations. The results show that this relation is linear and can be explained by a progressive accumulation of the plastic deformations, reducing the voids and increasing the rigidity of the material. This proves that, in situ, the modulus varies with the repetition of traffic and this behavior is important for predicting the modulus for pavement rehabilitation. The moduli do not show large variations with the number of load cycles but increase with the thickness of the base layer. Plastic deformation decreases with increasing modulus of the material and the modulus itself increases with the thickness of the layer. Between 20 cm and 30 cm, permanent deformation decreases slightly, but the modulus after 10,000 cycles increases about 35%. To predict the plastic strain of unbound layers under repetitive loading, regression models are proposed.