Abstract
Design methods of flexible pavements in many countries are based on linear elastic behaviour model for Unbound Granular Materials (UGM). In this context, parameters required to characterize an UGM in structural analysis of pavements are Stiffness modulus and Poisson ratio (E and ν). This paper presents a study of two UGM stiffness. Finite element simulation of repeated load CBR (RL-CBR) test has allowed to derive equation used in calculation of materials equivalent modulus based on laboratory RL-CBR Outputs. The staged RL-CBR test is used to evaluate material stiffness for different stress states to highlight its influence on UGM stiffness and compare studied materials. Also, this paper shows that even if two materials are different according to the current road authority specifications, they can represent similar stiffness.
Highlights
Characterization of Unbound Granular Materials (UGM) in Morocco and many other countries is based on standard tests like gradation, Sand Equivalent, Los Angeles, Micro-Deval and Plasticity Index... etc, which are not enough to evaluate UGM stiffness with efficiency
The standard identification conducted in LPEE laboratories shows that G-BS is a GNA and G-TM is a GNF2 according to Moroccan Catalogue [5]
Specimens are compacted with respect of its Optimum Moisture Content (OMC) determined by Modified Proctor test and a density equal to 98% of the Optimum Dry Density (ODD)
Summary
Characterization of UGM in Morocco and many other countries is based on standard tests like gradation, Sand Equivalent, Los Angeles, Micro-Deval and Plasticity Index... etc, which are not enough to evaluate UGM stiffness with efficiency. RL-CBR can be used to study mechanical behaviour of unbound or bound materials: resilient behaviour and resistance to permanent deformation This test is very simple and Its principle is similar to that of the well-known CBR test but repeated load is applied [4]. To transform this test to a triaxial one Araya and all [7] has equipped the mould by strain gauges to measure the mould lateral deformation ant have access to the lateral stress, a statistic analysis results makes possible the estimation of: mean vertical stress, lateral stress, Poisson ratio and the equivalent stiffness modulus based linear elastic theory in the triaxial stat of stress
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