Bench-Scale Investigation of Remote Detection of Clay Pockets in Granular Soils

The detection of deleterious materials in compacted soil fills is an important part of earthwork construction. These materials are often identified a priori using laboratory techniques such as the visual assessment of sieve analyses. However, it is possible that deleterious materials, such as clay pockets, can be larger than particles characterized in laboratory tests. Bench scale imaging using simulated unmanned aerial vehicle flights were conducted to determine if clay pockets, 15.24 cm by 15.24 cm by 5 cm thick, could be detected in granular soils. The imaging techniques employed were digital imaging, thermal imaging, and electromagnetic imaging. All imaging techniques could be used to identify clay pockets at the surface, but only electromagnetic imaging could detect clay pockets beneath the surface. The clay pockets were easily identifiable at depths of 2.5 cm and 15.2 cm in fine sand. When buried in pea gravel, the clay pockets were identifiable only at a depth of 2.5 cm. The clay pockets could not be identified when buried in gravel sized particles.