Impacts of Tensile Strength and Spacing of Geogrids on the Compressive Strength and Deformation of Reinforced Sand in Triaxial Compression
Behaviours of reinforced soil are affected by the ultimate tensile strength (Tult) of geogrid and the vertical spacing (Sv) of arrangement. Basically, the concept inferred from the current design approach of a reinforced-soil retaining wall shows that, if the Tult-to-Sv (or TVR) ratio is kept the same, the outcoming performance is also the same. In this research, a series of triaxial compression tests was performed with sand either unreinforced or reinforced with polypropylene geogrids having four different Tult values. Number of geogrid layers and Sv were adjusted so as to obtain three different TVR values. Effects of varying Tult and TVR values were studied by comparing the compressive strength (Rmax) and Poisson’s ratio (nsec) among different geogrid-reinforced sand samples. From the results of this study, the followings are found. By comparing at the same TVR, the Rmax decreases, while the nsec increases or the lateral deformation increases, with increasing Tult. This implies that the performance of reinforcing with the geogrids having lower Tult but are closely spaced is better than that of reinforcing with the geogrids having higher Tult but are coarsely spaced. On the other hand, when comparing at the same Tult, the Rmax increases, while the nsec decreases, with increasing TVR, because of the increasing of reinforcing density. The influences of Tult and TVR on the Rmax and nsec can be explained by the development of deterministic zone resulted from no connection between the geogrid and facing at the end, which negatively affect the transferring of the tensile force mobilised in the geogrid to additional confining pressure to sand.