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This technical note describes a comparison between the results obtained from single-stage and multistage ring shear tests on two different types of normally consolidated clay. The results confirm the brittle behavior of normally consolidated soils containing a high proportion of clay particles and the curved nature of the residual stress failure envelope. Detailed examination of the test data shows that while the multistage technique offers a considerable advantage in terms of the test duration, it may give erroneous results for soils with a high proportion of platy clay particles.

The main function of a pavement is to distribute the traffic-induced load over its different layers. While the flexible pavement design methods are based on a linear elastic calculation, the real behavior of the different layers is highly non-linear and elastic. They can also, in some cases, be plastic and viscous. This research aims to develop a three-dimensional numerical model that is closely similar to the test FWTT conditions. The model will have a real geometry wheel footprint (rather than a rectangular shape). As a substitute for incremental loading, the wheel movement during its passage over the specimen will be simulated by a horizontal displacement. These important characteristics of the model represent the novelty and the major difference between the current research and previous studies. The current model, which is based on the finite elements method, uses Abaqus software and a viscoelastic constitutive model. The materials' viscoelastic properties have been described by the Prony series, also called the relaxation modulus, which is a function of time. This parameter can be defined in most computer-aided engineering (CAE) software. The procedure for calculating the Prony series from experimental data is explained. The results obtained agree with the stress signal amplitude, the stress rotation principal, and the total displacement rotation when the load approaches the node considered and located in the middle of the specimen. Doi: 10.28991/CEJ-2022-08-03-03 Full Text: PDF