Modelling in situ shear strength testing of asphalt concrete pavements using the finite element method

Rutting is one of the well-recognized road surface distresses in asphalt co ncrete pavements that can affect the pavement service life and traffic safe ty. Previous studies have shown that the shear strength of asphalt concrete pavements is a fundamental property in resisting rutting. Laboratory inves tigation has shown that improving the shear strength of the asphalt concret e mix can reduce surface rutting by more than 30%, and the SUPERPAVE mix de sign method has acknowledged the importance of the shear resistance of asph alt mixes as a fundamental property in resisting deformation of the pavemen t. An in situ shear strength testing facility was developed at Carleton Uni versity, and a more advanced version of this facility is currently under de velopment in cooperation with the Transportation Research Board and the Ont ario Ministry of Transportation. In using this facility, a circular area of the pavement surface is forced to rotate about a normal axis by applying a torque on a circular plate bonded to the surface. The pavement shear stren gth is then related to the maximum torque. This problem has been solved mat hematically in the literature for a linear, homogeneous, and isotropic mate rial. However, the models for other material properties are mathematically complicated and are not applicable to all cases of material properties. The refore, developing a model that can accurately analyze the behaviour of asp halt concrete pavements during the in situ shear test has proven pivotal. T his paper presents the development of a three-dimensional finite element mo del that can simulate the forces applied while measuring the shear strength of the asphalt concrete pavement. A comparison between the model results a nd those obtained from available analytical models and field measurements p roved the accuracy of the developed model.