Aeolian sand widespread in the arid and semi-arid regions has been taken use as the cost-optimal subgrade filling materials. Under the drought climate, the performance of the compacted aeolian sand subgrade is largely dependent on its unsaturated strength. In this work, the shear strength with respect to the matric suction of unsaturated aeolian sand was investigated. A series of triaxial tests were conducted on the compacted specimens with different matric suctions. Results showed that the shear strength of specimen firstly increased with matric suction and then dropped off to a certain value. The maximum shear strength was reached at the matric suction of 40 kPa, which locates in the residual zone on the soil-water characteristic curve (SWCC) of the tested soil. Such phenomena were analysed from the perspective of capillary pore distribution, as well as the internal tri-phase (air-water-solid) structure that identified by microfocus X-ray computed tomography (mu CT) technique. According to the capillary pore size distribution of the specimen, pores with radius smaller than 21 mu m are theoretically saturated with water at suction of 10 kPa. The identified delimiting pore radius was found to be comparable to that of 25 mu m as identified by mu CT. On this basis, the role of water bridges in unsaturated aeolian sand and the pore size-level that govern the mechanical properties were discussed.

The cultural heritage sector has increasingly explored the use of micro-CT (mu CT) across numerous projects seeking to better understand past cultures and the materials they have left behind. As such, the role of micro-CT (mu CT) is still being developed and projects continue to show novel ways that the technology can be adapted to. The Gjellestad ship, located in Halden (ostfold in Viken), Norway, is dated to the Viking Age and was found in a poor state of preservation. Both organic and metallic materials were deteriorated to the degree that standard excavation methods would have resulted in further damage to, or even the destruction of, these elements. A new approach was needed, and this presented an opportunity to explore the use for mu CT as a documentative tool for field archaeology and conservation. As the remaining rivets were too fragile to handle directly, they were removed together with the surrounding matrix as soil blocks. To retain important stratigraphic and position information, a georeferencing system was developed that would be visible to mu CT and included within each soil block. This enabled the spatial (re)positioning of the soil blocks by use of 3D GIS and in alongside with other spatial documentation gathered at the time of excavation. The quantity of soil blocks will give us a large dataset to work with and, although we continue to document the soil blocks with mu CT, we now can discuss our preliminary results pertaining to the positive impact that mu CT has for the documentation, conservation, and reconstruction of cultural heritage.(c) 2023 The Author(s). Published by Elsevier Masson SAS on behalf of Consiglio Nazionale delle Ricerche (CNR).

The role of particle shape on soil mechanical response has been studied extensively especially through numerical means. The underlying micromechanics of how particle shape may affect the soil mechanical responses at element scale remains unclear. Systematic micromechanical experiments that consider in situ tracking of the evolution of fabric during the shearing process is missing. Aided by a miniaturised triaxial apparatus and X-ray computed tomography (CT), this study presents a series of triaxial compression on four granular soils with different particle shapes yet the same mineralogy, grading, and initial density. Evolution of three-dimensional soil fabric quantifiers during shearing was captured based on 192 full-field CT images. The results revealed that the initial shearing reduced the packing density without changing the particle packing pattern, followed by particle sliding and particle rotation, which redistributed the force chains and formed a new packing pattern to resist shearing, causing strain localisation, and reductions in both the contact number and concentration of contacts direction. Fabric anisotropy increased before reaching the peak and attained the maximum value as the soil approached the critical state. Particle shape, especially when quantified by overall regularity or other combinations of descriptors, displayed more significant linear correlations with critical-state parameters than by local descriptor.