Effect of Anisotropy on the Resilient Behaviour of a Granular Material in Low Traffic Pavement

Abstract

Granular materials are often used in pavement structures. The influence of anisotropy on the mechanical behaviour of granular materials is very important. The coupled effects of water content and fine content usually lead to more complex anisotropic behaviour. With a repeated load triaxial test (RLTT), it is possible to measure the anisotropic deformation behaviour of granular materials. This article initially presents an experimental study of the resilient repeated load response of a compacted clayey natural sand with three fine contents and different water contents. Based on anisotropic behaviour, the non-linear resilient model (Boyce model) is improved by the radial anisotropy coefficient γ3 instead of the axial anisotropy coefficient γ1. The results from both approaches (γ1 and γ3) are compared with the measured volumetric and deviatoric responses. These results confirm the capacity of the improved model to capture the general trend of the experiments. Finally, finite element calculations are performed with CAST3M in order to validate the improvement of the modified Boyce model (from γ1 to γ3). The modelling results indicate that the modified Boyce model with γ3 is more widely available in different water contents and different fine contents for this granular material. Besides, based on the results, the coupled effects of water content and fine content on the deflection of the structures can also be observed.

Hydro-Mechanical Behaviour of an Unbound Granular Base Course Material Used in Low Traffic Pavements

“…In this section, the proposed/modified models for permanent behaviour [4] and resilient behaviour [5] based on the researches for Missillac sand will be verified with the test results (RLTT and SWRC) of UGM Bréfauchet as follows.…”

“…where, K a , G a , and n are parameters; γ 1 is the axial anisotropy coefficient, γ 1 = |ε 1 /ε 3 |; p a is 100 kPa. Based on the results of Missillac sand, the radial anisotropy coefficient γ 3 was suggested by authors [5] to replace the axial anisotropy coefficient γ 1 to fit the changing anisotropy behaviour of granular materials under the repeated loading. The improved model was expressed as…”

“…In recent years, the effect of moisture content on deformation behaviour, which was equally important, has been studied by many researchers [4][5][6][7][8][9][10][11][12][13]. These researches showed that the permanent or resilient deformations increased with water content and different prediction models were proposed to evaluate the deformation behaviour of unbound granular materials.…”

“…Especially, based on a long-term research on a subgrade material-Missillac sand (Missillac sand is an alluvium sand coming from the quarry of Missillac in France), authors [4] suggested two approaches (water content and fine content method/suction method) to predict the permanent deformation with different water contents and different fine contents. For the resilient behaviour, an improved Boyce-Hornych model [5] has shown that it has a good adaption to the changing anisotropy caused by the various water contents or fine contents under repeated loading. However, these findings were obtained just based on only one granular material-Missillac sand and the further verification with other materials for the general equations was greatly required.…”

Test Granular Materials Failure Using Bi-Directional Simple Shear Apparatus: A Review

“…Soil that mainly includes sand and clay is a widely available natural granular material, and it has been extensively used and studied as a construction material in engineering [1][2][3][4][5][6][7][8][9][10]. However, because of the complexity of soils, the behaviour, especially the shear behaviour, is not well understood yet, in terms of research and construction.…”