Shear strength and permanent deformation of unbound aggregates used in brazilian pavements

摘要

Most of studies on unbound aggregates carried out in Brazil have discussed elastic behaviour and little attention has been paid to shear strength and permanent deformation. This paper analyses the results of a laboratory study on the strength and permanent deformation characteristics of unbound aggregates used as bases or sub-bases in Brazil. Three gradations (one well-graded and two open-graded) were chosen, in order to quantify the effects of fine aggregates (percent passing in a #4 sieve), stress state on shear strength and permanent deformation. Failure envelopes and shear strength parameters (c' & φ') were obtained in triaxial tests and permanent deformation evolution was measured under dynamic loading. Models relating permanent deformation to number of loading cycles and stress state are proposed and the permanent deformation evolutions of the three gradations are compared. Global results show that the well-graded aggregates presented higher strength and accumulated lower deformation than the open ones.