The effect of maximum diameter of geogrid-reinforced sandy soil particles on shear strength parameters

Abstract

Geogrid reinforcement is an effective method for improving the strength characteristics and bearing capacity of granular soils. The dimensional ratio of the diameter of soil particles to the mesh size of geogrid apertures can be effective on the strength performance and stress- deformation of the reinforced soil. To explore these factors, a sandy soil sample from Tonekabon (Iran) was separated into three gradations with a maximum particle diameter of 4.75, 2, and 0.425 mm, with an average relative density of about 57%. The samples were reinforced with two types of polyvinyl chloride (PVC) mesh as a geogrid, with aperture dimensions of 5 and 3 mm. All the samples were subjected to compressive loading in the triaxial shear apparatus under effective stress conditions. With a relative increase in the mesh size of the geogrid aperture to the maximum dimension of the reinforced soil grains, the internal friction angle decreased. Moreover, reinforcement of non-cohesive sandy soil caused apparent cohesion in the consolidated undrained conditions, and this was more evident with the reduction of the maximum diameter of sand particles. Decreasing the maximum diameter of the particles from 4.75 to 0.425 mm in the unreinforced and reinforced conditions caused the internal friction angle of the soil to drop by about 8%–10%. For the non-cohesive sandy soil, the results showed that soil reinforcement caused a more salient apparent cohesion in the soil with the maximum diameter of smaller particles. The sand passing through sieve #40 (0.425 mm) showed a cohesion of 0.2 to 0.34 kg/cm2 upon reinforcement with both types of meshes, while the soil lacked significant cohesion in the unreinforced conditions.