Using Synchrotron-Based X-Ray Microcomputed Tomography to Characterize Water Distribution in Compacted Soils

الملخص EN

Water plays a vital role on the hydromechanical behavior of unsaturated soils.

An important concern in unsaturated soil mechanics is to determine the distribution of water within voids and its interaction with soil grains.

This paper presents some results of the spatial distribution of water in different soils using the synchrotron-based X-ray microcomputed tomography (μ-CT).

Three materials (glass beads, natural sand, and clay) were first prepared at a water content of about 10%, statically compacted under vertical total stress of 500 kPa, and then scanned by synchrotron X-rays at an energy of 18 or 20 keV.

The three-dimensional (3D) microstructure of the samples including air, liquid, and solid phases was reconstructed, and some new observations were obtained: (i) the iodine-based contrast medium (KI) can increase the peak greyscale value of water from 110 to 122, enhance the air-water contrast, and thus facilitate the segmentation of water phase; (ii) in the compacted glass beads and sand, water distribution is characterized using the μ-CT and image reconstruction technique.

The water contents obtained by phase segmentation, i.e., 10.2% and 9.3%, are comparable with those measured by the oven-drying method, i.e., 9.7% and 9.4% for the glass beads and sand, respectively; (iii) water is preferably distributed within aggregates when it is mixed with the oven-dried particles, and an aggregate-dominated 3D structure is observed.

However, it is impossible to determine the water phase for the studied material even with the resolution of 0.65 μm/pixel.