Abstract: Geogrid has been widely used in various practical reinforced soil structures, and are more or less in plane strain conditions. In order to describe the compound stress-strain behavior of geogrid reinforced soil under plane strain conditions and to improve the understanding of geogrid reinforcement mechanisms, large-scale biaxial compression tests were carried out on granular soil and geogrids with different numbers of transverse members. The influence of geogrid transverse members on the strength and deformation behavior of reinforced soil was investigated. The experimental results showed that the maximum vertical stresses of reinforced soil specimens were greatly improved using geogrid reinforcements. With increasing number of geogrid transverse members, the maximum vertical stress of reinforced soil specimen increased. Using the Digital Image Correlation (DIC) method, the displacements and rotations of soil particles in the unreinforced and reinforced specimens under the same confining stress were achieved to visualize the geogrid reinforcing effects. Moreover, the maximum longitudinal geogrid tensile strain in each reinforced specimen under biaxial compression loads occurred in the middle part of the geogrid and decreased gradually from the middle part to the side boundaries of the geogrid. Under the same vertical strain, the tensile strains within the upper geogrids were slightly larger than those within the lower geogrids. The longitudinal tensile strains decreased with increasing number of geogrid transverse members under the same vertical stress.

Key words: geogrid, transverse member, granular soil, plane strain, digital image correlation (DIC)