عنوان مقاله [English]
Coastal sandy soils cover a large part of the soil of northern part of the country. These soils will have problems due to loose characteristic and lack of proper strength properties for roads building. Beach sand is encountered with the wash-out phenomenon due to uniform gradation and lack of cohesion at the time of the water flow in an unconfined state. To solve the problem of these soils, various methods such as reinforcement with different materials are used. In this research, the effect of adding various percentages of polypropylene fibers to non-cemented and cemented sand on the mechanical characteristics of sandy soils of Babolsar beach was investigated by performing direct shear tests and triaxial tests. According to the results, adding these fibers improves the internal friction angle, cohesion, maximum strength, Failure strain and residual strength of sand. Comparison of the results of direct shear tests and triaxial tests showed that, due to the proper orientation of the fibers relative to the direction of main tensile strains in triaxial tests, the efficiency and their effect on the soil resistance behavior in triaxial samples were more significant than direct shear tests.