Triaxial Testing on Geogrid-reinforced Granular Soils

Abstract

Laboratory triaxial compression tests were carried out to investigate the mechanical behavior of dense sand and geogrid-reinforced granular soils. The tested sand having its mean particle size (D50) equal to 0.6 mm was adopted. Three geogrids with different longitudinal and transverse nominal strengths were used. The dimensions of the cylindrical soil specimen were 70 mm (diameter) × 160 mm (height). The relative density was equal to 70% for all tests. The reinforced sand specimens with one or two geogrid layers were sheared under effective confining pressures (σ′3) equal to 50 kPa. The test results of unreinforced sand indicate the general stress-strain behavior of dense sand when sheared, whereas the deviatoric stress reaches its peak value, after which it gradually decreases to ultimate value (σ1 - σ3)ult. The difference of effective confining pressure indicates that the peak of deviatoric stress Δσd = (σ1 - σ3) increases with the increase in effective confining pressure (σ′3), while the peak principal stress ratio (σ′1/σ′3) decreases with the increase (σ′3). The friction angle (ϕ′)and cohesion (c′), defined by analytical and graphical methods for unreinforced sand. Geogrid as reinforcement increasing peak shear strength. The increasing peak shear strength is more pronounced with a higher number of geogrid and the geogrid with higher stiffness. Increased in confining stress inside reinforced soil mass (Δσ3R) can be interpreted by cohesive reinforced soil (CR).

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

“…This phenomenon was more obvious in fine-grained sands. Similar laboratory studies and results regarding the performance of reinforced sands in triaxial shear apparatus have been reported by Moghaddas and Asakereh (2007), Khaniki and Daliri (2012), Mindiastiwi et al (2021), Skuodis et al (2020), and Yi and Du (2020) [5,6,8,17,18].…”

“…Given the higher growth rate of cohesion in the reinforcer with an aperture dimension of 5 mm and a thickness of 2 mm compared to the one with an aperture dimension of 3 mm and a thickness of 1 mm, we observe the positive effect of the tensile strength of the reinforcer on the cohesion growth, as reported by Mindiastiwi et al 2021; Yi, F. and Du, C., 2020; Skuodis et al 2020. They have concluded that the increasing peak shear strength is more pronounced with a higher number of geogrid and the geogrid with higher stiffness [8].…”

“…This agrees with investigation of Mindiastiwi et al, 2021. They believe, the mechanism of the development of cohesion is due to the increased confining stress generated in the soil due to the membrane stress in the wall of geogrids [8].…”

“…Various elements, including natural cellulose or carbonate fibers such as plant roots, human and animal hair, woven or non-woven synthetic fibers made of glass, steel, polypropylene, polyethylene, and polyester in the form of geocomposites, geotextiles, geogrids, geosynthetics, geomembranes, etc have been incorporated for soil reinforcement [4][5][6][7]. Geogrids are one such reinforcing element, widely used in soil reinforcement to increase the bearing capacity and reduce settlement by improving the shear strength and deformation parameters of the soil [8]. The most common deformation and failure criteria in soils are Young's Modulus and two strength parameters, including cohesion and internal friction angle.…”

Triaxial Test of Coarse-Grained Soils Reinforced with One Layer of Geogrid

“…The results obtained showed that the geogrid creates apparent cohesion and a small change in the angle of internal friction [32]. The effect of the geogrid is better reflected through the reinforcement effect, which is expressed as the ratio of the maximum deviatoric stress with the geogrid to the maximum deviatoric stress without the geogrid [33]. Obtained results depend on the type of soil, the type of geogrid, and the confining pressure at which the tests were carried out [34].…”