Abstract

Estuarine tidal flats represent a critical environment for maintaining healthy ecosystems. The geotechnical characterization of such environments is often challenging due to their soft nature and remote locations. Thus, the goal of this study is to explore the use of remotely sensed, high resolution (pixel resolution of ~0.5 m) synthetic aperture radar (SAR) data for characterizing these sediments. Towards this goal, the variability of sediment properties (median gain size, moisture content, fines content, and classification following the Unified Soil Classification System (USCS) were documented for a mixed tidal flat located on the Great Bay Esturay in New Hampshire, USA. A sediment classification scheme based on SAR, originally proposed by Gade et al. (2008), which utilizes the correlation length to characterize sediments based on the percentage of particles <0.063 mm, was tested using a high-resolution X-band SAR image (pixels of ~0.5 m) collected simultaneously to in situ measurements and a medium-resolution C-band image (pixels of ~10 m) collected 3 days later. The results of this study demonstrate that the framework proposed by Gade et al. (2008) was generally able to predict the correct soil classification for coarser sediments but failed to predict the correct soil classification for finer sediments when applying the original image resolutions. When the X-band image was downsampled to match the C-band image resolution, the framework was still unable to predict the expected soil classification. This suggests that, in order to utilize high-resolution X-band data to predict soil type, alternative sediment type classification schemes are required.

Abstract

This paper investigated cone penetration test end resistance under various drainage conditions in mixed soils through numerical simulations and piezocone experiments in laboratory testing chambers. The soil samples used in the laboratory tests contained various proportions of kaolin, silt, and sand. The piezocone tests were performed using a 10 mm diameter cone in consolidated soil samples. The measured variations of cone resistance and pore pressure at cone velocities varying from 0.005 mm/s to 30 mm/s are presented, which covered the full range from drained to undrained conditions. The cone resistance was evaluated using the spherical cavity expansion limit pressure predicted in Finite Element (FE) analyses that employed the NorSand (NS) constitutive model. The experimental and numerical findings allow assessment of the suitability of the normalised velocity (V) term, proposed by others, to unify cone resistances measured at variable rates.