Accurate characterization of the stress-strain properties of geomaterials is key to predicting the durability and lifespan of pavement systems rigorously. The geomechanical properties of these materials are typically evaluated using standardized laboratory tests, such as the California Bearing Ratio (CBR) and the standard resilient modulus (MR). However, a significant challenge emerges since standard MR tests performed in the laboratory fail to mimic the loading conditions encountered in the field and also lack in adequately characterizing the behavior of geomaterials under these loading conditions. This divergence between laboratory methods and actual field conditions can result in inaccurate predictions of stiffness and the permanent deformation characteristics of pavement foundation layers i.e. base, subbase, and subgrade. A major aspect leading to pavement performance challenges linked to material characterization stems from the fact that geomaterials used in foundation layers exhibit cross-anisotropic behavior where deformation characteristics are direction dependent. Given the complex nature of traffic loading where the continuous principal stress rotation occurs there's a growing need to determine the mechanical properties in the horizontal direction. Furthermore, the stiffness and plastic deformation of these geomaterials are greatly influenced by freeze-thaw (F-T) cycles. This aspect, combined with the directional dependency, highlights the complex response of these materials under varying conditions, emphasizing the need for more comprehensive testing and modeling approaches. While laboratory analysis offers essential insights into the mechanical properties of materials, it's well-established that the behavior of geomaterials heavily depends on the moisture content they encounter throughout a pavement's service life. The moisture levels in these foundation layers, including the base, subbase, and subgrade, are subject to variations due to environmental factors such as groundwater table changes, F-T action, and shifts in climatic conditions. As a result, the field monitoring of moisture becomes critically important. In this study, the cross-anisotropic mechanical behavior of various geomaterials under stress conditions mimicking the field was examined. This examination involved determining cross-anisotropy ratios to better understand the extent of observed cross-anisotropy. Additionally, advanced testing, simulating field conditions, was conducted to explore how F-T cycles impact geomaterial behavior. To ensure reliable moisture monitoring, innovative installation methods and soil-generic calibration equations were developed for moisture sensors installed in the field. A preliminary analysis was conducted using the data collected from these sensors.
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