Identification and discussion on distress mechanisms of unsurfaced gravel roads: Fid-Bau Portal

Identification and discussion on distress mechanisms of unsurfaced gravel roads

Nervis, Leandro Olivio / Nuñez, Washington Peres

Abstract Most of Brazilian and other countries’ road networks mainly comprise unsurfaced gravel roads. The maintenance of such roads at a minimum acceptable level of serviceability consumes large percentages of government budgets. In spite of that, the construction and maintenance activities hardly ever succeed, since the personnel involved do not know the specific technology. Aiming at contributing towards more effective practices, this paper analyses the results of a research carried out with the objective of identifying and discussing distress mechanisms of unsurfaced gravel roads, based on Soil Mechanics. Experimental procedures included laboratory tests, as well as the construction and performance monitoring, along 30 months, of a test section, in an agrarian reform settlement, in southern Brazil. The wearing course of the unsurfaced pavement consisted of two different layers (a 7-cm-thick upper layer, made of sandy gravel and a lower one with 17 cm of lateritic clay), built over a stratified subgrade, with a sandy upper layer. Layer compaction was quantified by means of classic tests. Samples were taken from the subgrade and from both materials that constitute the wearing course, in order to perform laboratory tests. During the monitoring period three roughness (IRI) surveys were carried out, using an inertial profilometer. Four distress surveys were carried out to evaluate the evolution of the most important distresses of unsurfaced gravel roads. Rutting, potholes, cross-section deformation and thickness reduction and erosion channels were observed and the associated distress mechanisms were discussed.