Impact of fines on the accumulated strain of unsaturated road base aggregate under cyclic loadings

The property of a road base depends on its fine content (FC) and water content/suction. In this study, a cyclic loading test was carried out on road base aggregate with different FCs under controlled suction. The different effects of fines on the accumulated strain of road base aggregate at different FCs and suctions were identified. Under the saturated condition, the accumulated strain increased with FC due to the reduction of soil interparticle friction caused by the inclusion of fines. Under unsaturated conditions, the effect of fines on the accumulated strain depended on the inner structure of the soil. For the 'coarse-graincontrolled soil' (FC in the range of 0%-4%), the accumulated strain increased with the increase of FC due to the reduction of interparticle friction, while for the 'transition soil' (FC in the range of 4%-8%), the accumulated strain decreased with the increase of FC as the major impact of the fines shifted to the enhancement of suction, and the inclusion of fines is beneficial for this case; for the 'fine-grain-controlled soil' (FC in the range of 8%-16%), the accumulated strain increased rapidly with FC as the effect of interparticle friction reduction dominated again. Key words: road base aggregate, fine content, cyclic loading, accumulated strain, unsaturated soil La propriete de la base de la route depend de sa teneur en fines (FC) et de sa teneur en eau/suction. Dans cette etude, l'essai de chargement cyclique a ete effectue sur un agregat de base de route avec differentes teneurs en fines sous des succions controlees. Les differents effets des fines sur la deformation accumulee du granulat de la base de la route a differentes teneurs en fines et suctions ont ete identifies. Dans des conditions de saturation, la deformation accumulee augmente avec la teneur en fines en raison de la reduction de la friction interparticulaire du sol causee par l'inclusion de fines. Dans des conditions non saturees, l'effet des fines sur la deformation accumulee depend de la structure interne du sol. Pour le << sol a gros grains controles (FC dans la gamme de 0-4 %)>>, la deformation accumulee augmente avec l'augmentation de la teneur en fines en raison de la reduction de la friction interparticulaire; tandis que pour le << sol de transition (FC dans la gamme de 4-8%)>>, la deformation accumulee diminue avec l'augmentation de la teneur en fines comme l'impact majeur des fines se deplace vers l'amelioration de la succion, et l'inclusion de fines sera benefique pour ce cas; pour le << sol a grains fins controles (FC dans la gamme de 8-16%)>>, la deformation accumulee augmente rapidement avec la teneur en fines, car l'effet de la reduction de la friction interparticulaire domine a nouveau. [Traduit par la Redaction] Mots-cles : agregat de base de route, teneur en fines, chargement cyclique, deformation accumulee, sol non sature
Introduction Road base aggregates mainly consist of unbound granular materials such as gravel and sand. During a road's service, the road base aggregate can be invaded by fines from particle [...]