| dc.description.abstract | Flexible pavements consist of the asphalt concrete layer, base layer and subbase layer, and these three layers are made of asphalt concrete, unbound granular aggregates and compacted soils, respectively. In flexible pavements, there are two main distresses, fatigue cracking and rutting. Fatigue cracking only happens in the asphalt concrete layer, while rutting can occur in every layer. The distress development is related to the material properties in each layer.
In Chapters 2-4, three energy-based models are proposed to predict the fatigue cracking in asphalt concrete and plastic deformation in asphalt concrete and unbound granular aggregates. In the fatigue cracking model, the damage evolution is connected with the mass specific volume of asphalt concrete, so the model is independent of the reference configuration. In the rutting model for asphalt concrete, the proposed model is incorporated into a framework. In this framework, the mechanical properties of asphalt concrete can be obtained from its microstructure and properties of its components. The effects of temperature, aging and seasonal changing of rutting resistance are considered. In the rutting model for unbound granular aggregates, the effects of moisture and microstructure of the material are considered. By doing numerical simulation and comparing model predictions with test data, the proposed models can capture the distress development accurately.
In the fifth chapter, a micromechanics model for soils is proposed to predict the soil-water characteristic curve (SWCC), and this curve plays an important role on the prediction of soils’ performance. The proposed model can account for the adsorption and capillary contributions on the accumulation of water in soils. The contact angle hysteresis is considered to capture the SWCC hysteresis, and the concept of equivalent grain radius is proposed to consider the effect of grain-size distribution. Every parameter in the model has a clear physical meaning and is measurable easily. The proposed model can capture the SWCC well, and model predictions show that positive and negative matric suction contribute to the shrinkage and swelling of expansive soils respectively.
The last chapter summarizes the main findings. | |
