Study of the permanent deformation of three soils employed in highway subgrades in the municipality of Santa Maria-RS, Brazil.

Permanent deformation is associated with wheel track rutting (WTR) and is one of the main causes of defects in the pavements of Brazilian highways. Seeking to mitigate this situation, this paper presents a study about the permanent deformation of three typical subgrade soils of the Santa Maria region, Rio Grande do Sul (RS), located in the southern region of Brazil. In addition to the physical, chemical, and mechanical characterization of the materials, this research presents results from repeated load triaxial tests to obtain the resilient modulus (RM) and the permanent deformation (PD) parameters. The Compound model of the resilient modulus, posteriorly cited on the Petrobras Asphalt Thematic Network Project, showed the best results. The permanent deformation tests were conducted using a frequency of 2 Hz and 150,000 load application cycles and posteriorly adjusted to the Guimarães Model, of which average statistical correlation was 0.91. However, the predominance of fine materials combined with low compaction energy resulted in high deformation rates and the occurrence of shakedown in domains: A (plastic shakedown), B (plastic creep) and C (incremental collapse). [ABSTRACT FROM AUTHOR]