Analytical prediction of soil–water characteristics curves for granular pavement base course materials

The soil–water characteristic curve (SWCC) plays an important role on predicting performance of granular materials. To consider the effects of material structure and water contact angle hysteresis on the SWCC, a new model is proposed. In the model, the material structure is divided into the primary structure (PS) and the secondary structure (SS). PS and SS are determined based on the grain-size distribution of materials, and compared with SS, PS is composed of larger particles forming the load transferring network in materials. It is assumed that water films mainly exist in the PS, while liquid bridges mainly exist in the SS. Thus, the residual water content is determined based on the PS, and the liquid bridge volume between particles is determined from the total water content of materials based on SS. Then, a new liquid bridge model is proposed to determine the suction between two particles based on the liquid bridge volume. Due to the water contact angle hysteresis, the advancing and receding contact angles are used to derive the wetting and drying SWCC curves, respectively. Some test data are used to verify the proposed model. It is found that the model predictions match the test data well, and the SWCC hysteresis is captured by considering the contact angle hysteresis.