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A new testing system for determining soil particle size distributions (PSDs) is under development. It augments existing systems generically called “SedImaging” by the addition of a water pressure transducer near the bottom of a soil sedimentation column. The original SedImaging test provides image-based PSDs for sands, while the pressure transducer will extend the PSDs into the silt range. The new test system is called the “uSed” reflecting the measurement of water pressures (u) during a SedImaging test. This paper presents the uSed theoretical equations and the results of four pilot tests on sands to verify the theory. The four specimens were coarse sand, medium-sized sand, fine sand, and a gap-graded sand. The observed pressure decay curves were qualitatively as expected and the masses of solids predicted by the uSed theory agreed with the actual specimen masses to within an error of 2%. 

This paper introduces a new paradigm that integrates the concepts of particle abrasion and breakage. Both processes can co-occur under loading as soil particles are subjected to friction as well as collisions between particles. Therefore, the significance of this integrating paradigm lies in its ability to address both abrasion and breakage in a single framework. The new paradigm is mapped out in a framework called the particle geometry space. The x-axis corresponds to the surface-area-to-volume ratio (A/V), while the y-axis represents volume (V). This space facilitates a holistic characterization of the four-particle geometry features, that is, shape (β) and size (D) as well as surface area (A) and volume (V). Three distinct paths (abrasion, breakage, and equally occurring abrasion and breakage processes), three limit lines (breakage line, sphere line, and average shape-conserving line), and five different zones are defined in the particle geometry space. Consequently, this approach enables us to systematically relate the extent of co-occurring abrasion and breakage to the particle geometry evolution.