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University of Arizona (1973)

FATIGUE CHARACTERISTICS OF AN ASPHALT STABILIZED DUNE SAND

Al Salloum, Nasser Mohammad

Titre : FATIGUE CHARACTERISTICS OF AN ASPHALT STABILIZED DUNE SAND

Auteur : Al Salloum, Nasser Mohammad

Université de soutenance : University of Arizona

Grade : Doctor of Philosophy (PhD) 1973

Résumé partiel
Most pavement design methods consider static loading conditions in designing and evaluating pavements whereas failure in roads is caused mainly by excessive repeated flexural stresses. The behavior of stabilized materials under repeated actions of loads is an aspect of design that, until recently, has not received much consideration. The aim of this investigation is to study the behavior of an asphalt stabi lized soil subjected to repetitive flexural stresses. Wind-blown sand is chosen for this study owing to the fact that the surface of most of the world’s deserts consists largely of dune sands with little or no natural suitable road construction materials available. Samples \1\ in. in diameter, manufactured by the Jimenez knead ing compactor, were tested in the Jimenez def1ectometer machine, which is essentially a controlled stress type, under controlled repetitive loading. Variables such as (1) asphalt content, (2) testing temperature, (3) initial support pressure, (4) radius of loaded area, and (5) speci men thickness were chosen, to study their effects on the fatigue charac teristics of the asphalt-stabilized dune sand. The study indicated that the resistance to fatigue failure in creases in a linear logarithmic relationship with the decrease in the testing temperature and with the increase in the specimen thickness and the radius of loaded area. The trend of the data indicates the exist ence of a linear relationship between the logarithm of the number of load repetitions to failure and the initial support pressure given to the specimen at the start of the test. Moreover, this’study shows the existence of an optimum asphalt content at which the number of load rep etitions to failure and the dynamic modulus of elasticity attain their maximum values. This optimum asphalt content value is unique in that the testing temperature has no effect on it. It is interesting to note that the optimum asphalt content for maximum fatigue life coincides with that obtained for maximum stability. Knowing the applied stress levels, the support pressures, spec imen thicknesses, loaded area, effective specimen diameter, measured repeated surface deflection, and Poisson’s ratio of the material, the radial stresses and the dynamic moduli of elasticity were computed using modifications to Grashof’s equations for stresses and deflections in a circular plate. These equations are based on the assumption that the material behaves elastically. The results of this dissertation indicate that the dynamic modu lus of elasticity is greatly affected by testing temperature, with which it has a linear logarithmic relationship. To a lesser degree, the dy namic modulus is also affected by specimen thickness, initial support pressure, radius of loaded area, and asphalt content. Moreover, this study indicates that there exists a linear logarithmic relationship be tween the fatigue life and both the radial stress and radial strain lev els. However, there is no evidence that the radial strain is the most governing factor in fatigue testing. It is believed that such a finding is attributable to the shear deformations resulting from test procedure

Mots clés : Road materials — Testing. ; Soil stabilization. ; Asphalt.

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