Description:
Unbound Granular Material (UGM) used in the base/subbase layers of a flexible pavement structure constitutes the vast majority of the material found in roads around the world. The permanent deformation of a compacted UGM layer due to cyclic deviatoric loading has a significant effect on the performance of the pavement structure. The accurate prediction of the magnitude of accumulated permanent strain at varying load cycles and stress levels plays an important role in improving the design and maintenance of flexible pavements. In this study, samples of two road base UGMs are tested to evaluate the characteristics of permanent deformation using the laboratory Repeated Load Triaxial (RLT) test. Three permanent deformation models are used to predict the magnitude of strain accumulation of the studied UGMs. The permanent strain results predicted by the models are compared against those measured by laboratory RLT tests to evaluate the prediction ability of each model.
Description:
Bearing Capacity of Roads, Railways and Airfields - Proceedings of the 10th International Conference on the Bearing Capacity of Roads, Railways and Airfields, BCRRA 2017
Description:
Unbound Granular Materials (UGMs) are used in the base/subbase layers of flexible pavement structures for the vast majority of the main roads around the world. The resilient modulus of UGMs is a key input parameter for the design and analysis of flexible pavement structures. In the present study, four road base UGMs with a range of moisture contents are used to evaluate each material's resilient deformation behaviour using laboratory repeated load triaxial tests. The triaxial system for the tests is instrumented with four axial deformation gauges: an on-specimen axial Hall-Effect transducer, an internal Linear Variable Differential Transformer (LVDT), an external LVDT, and the actuator LVDT. The application of a Hall-Effect transducer directly mounted on the specimen and the three LVDTs permits the comparative study of alternative deformation measurements for the determination of an accurate and reliable resilient modulus value. By comparing tests results obtained with each transducer, the relative capability of each measurement is determined and a reference transducer for deformation measurement is identified. A constitutive model is then used to carry out a regression analysis and to predict the resilient modulus of the four tested materials.