Evaluation of soil-geogrid interaction using transparent soil with laser illumination

An experimental methodology was developed involving techniques that allow non-intrusive measurement of confined geogrid deformations and soil particle displacements under pullout loading condition, which together are expected to generate a comprehensive volume of data including the entire displacement field in both geogrid and surrounding soil. The techniques involve the use of transparent soil with laser-aided imaging, which allows visualization and facilitates subsequent evaluation of the load-transfer mechanisms that develop between soil particles and the different rib elements in geogrids. A laser beam was employed to track the transparent soil particles in a plane perpendicular to the soil-geogrid interface. The collimated laser beam produced well-defined individual particles in the selected plane of the soil model. Digital cameras were used to track the displacement fields of both the confined geogrid specimen and soil particles within the laser-illuminated plane. Digital image correlation as well as other image-processing techniques were used to define the displacement fields based on images captured during the tests. The field displacements resulting after processing the data gathered from the newly developed experimental system led to well defined manifestations of the load transfer mechanisms, including the deflection patterns in geogrid ribs and shear bands within the soil mass.