عنوان مقاله [English]
In the last few decades, due to increasing the use of geosynthetic reinforcements in reinforcing the soil, the behavior of the soil-geosynthetic interface has considered by researchers. On the other hand, the use of geofoams in the form of block and/or bead, due to decrease the weight of the soil mass behind the retaining structures, has attracted the designers’ attention. In this regard, the current study has been done with the aim of determining the interaction parameters of soil containing geofoam beads and geosynthetic reinforcements. For this purpose, large-scale direct shear apparatus with box dimensions of 304.8*304.8*152 mm has been used. The used soil has been the mixture of Firoozkooh sand (#. 161) and geofoam beads with a diameter of 2 mm and the geofoam mix percentages have been selected as 0.2, 0.4 and 0.6 percent by weight of the soil. Also, the reinforcements used in this research have included of geogrid, geotextile and geocomposite that accordingly, further analysis and comparison of the obtained results can be possible. According to the results, in the sand-geofoam mixtures reinforced using geosynthetics, with increasing the mix percentage of geofoam, shear strength amounts have decreased. Also, in these mixtures, the greatest increase in bearing capacity comparing to corresponding unreinforced mixtures, has obtained for samples reinforced with geogrid and later, for samples reinforced with geocomposite and geotextile, respectively. In general, depending to reinforcement type and geofoam mix percentage, increase of bearing capacity in the reinforced mixtures with respect to unreinforced mixtures, has been about 12% to 135%. By increasing the mix percentage of geofoam from 0.2 to 0.6, the amount of this increase has decreased. In the sand-geofoam mixtures reinforced with geosynthetics, the highest interaction coefficient has obtained in the samples reinforced with geogrid, geocomposite and geotextile, respectively. In the sand-geofoam mixtures reinforced with geogrid, the highest of interaction coefficient, has observed in the geofoam of 0.4% and then, in the geofoam of 0.2%.