Single fiber pull-out test and the determination of critical fiber reinforcement length for fiber reinforced soil

The interfacial interaction between the fiber and soil matrix is a key parameter in controlling the strength behavior, physico-mechanical properties of fiber reinforced soil (FRS). Therefore characterization and analysis of the micromechanical behavior such as the interfacial shear strength. tau(f) is significant for investigating the mechanism of FRS and particular application to engineering. In order to assess and investigate the. tau(r) and interfacial residual shear strength. tau(f) of PP-fiber (polypropylene fiber) reinforced soil, the single fiber pull-out tests are carried out on the soil samples with different water contents and soil dry densities by using the tester designed by ourselves. The influence of water content and dry density on the tau(f) and tau(r) is analyzed. This investigation proves that the designed tester can be applied to single fiber pull-out test effectively; and the test results are exact. It is found that the. f and tr of samples are decreased with the increase of water content, while increased with an increase in soil dry density. The behavior of the force-displacement curves in the pull-out test depends ultimately on the intrinsic characteristics of the interface; and the shape is not significantly influenced by the water content and dry density. Finally, the critical fiber length is assessed by the obtained interfacial shear strength of fiber/soil.