Interface Properties of Metal-Grid and Geogrid Reinforcements with Sand

Abstract

Reinforced earth or soil structures are becoming increasingly popular in the present day. For proper design of any reinforced structure, it is important to study the soilreinforcement interface properties. The interaction mechanism can broadly be classified into two types: direct shear mechanism and pullout mechanism. In this study, tests were performed as per ASTM D5321 to study the interface characteristics of two types of reinforcements commonly used in practice (geogrid and metal grid) with Indian standard sand. A large-size direct shear test apparatus of dimensions equal to 300mm x 300mm x 200mm (in length, width and depth) is used in the study. Pluviation method is adopted to prepare uniform sand samples with a relative density of 90%. This paper provides details on sample preparation and interface properties of two types of reinforcements with sand material. Based on the test results, the average interface shear strength coefficients of geogrid-sand and metal grid-sand are found to be equal to 0.88 and 1.02 for the normal stresses considered in the study. These coefficients are in good agreement with the results reported in the literature.

Interface Shear Behavior of Geogrid-Reinforced Calcareous Sand Under Large-Scale Monotonic Direct Shear

“…Under different normal stresses (i.e., σ n = 25 kPa, 50 kPa, 75 kPa, and 100 kPa) and relative densities (i.e., D r = 50%, 70%, and 90%), the shear stress-displacement behavior of the GRCS and URCS interface basically show different degrees of strain-softening. This conclusion is consistent with Wang et al [25], Liu et al [38], Anubhav and Basudhar [39], Umashankar et al [40], Esterhuizen et al [41], and Seo et al [42]. From the perspective of normal stress, for example, when D r = 50% and the normal stress is 100 kPa, the peak shear stress of the geogrid-calcareous sand interface is 3.39 times that of when the normal stress is 25 kPa, and the corresponding displacement of the peak shear stress is 17.01 mm and 34.8 mm when the normal stress is 25 kPa and 100 kPa, respectively.…”

“…Abu-Farsakh and Coronel [46] discovered that the interface shear strength coefficient of geogrid-sand ranges from 0.90 to 1.05, and is suitable for various soil density and water content conditions. Similarly, Liu et al [38] pointed out that the shear strength coefficient Umashankar et al [40] concluded that the shear strength coefficient of the geogrid-sand interface ranged from 0.97 to 0.81. However, in this study, the R e under different relative densities and normal stresses are all greater than those above of terrigenous sand, indicating that the reinforcement effect of geogrid embedded in calcareous sand filler is more significant than that of terrigenous sand.…”

“…In addition, the R e declines with the increase of relative density, while the change is not obvious with the increase of normal stress. With the increase of normal stress, the curves of R e under three relative densities exhibit different development trends, reaching the maximum when the normal stress is 50 kPa Nevertheless, Umashankar et al [40] pointed out that the reinforcement effect coefficient of geogrid-sand and metal grid-sand declines with the increase of normal stress. He et al [44] carried out the direct shear test study of geogrid-reinforced clay, and found that the reinforcement effect coefficient was consistent with the research results of Umashankar et al [40].…”

Determining the Shear Strength Properties of a Soil-geogrid Interface Using a Large-scale Direct Shear Test Apparatus

“…The results also showed that the values of the coefficient a for Samples 2 and 3 are higher in the critical stress state. The higher values of the coefficient a for the critical state have been also presented by, e.g., [17].…”

“…The test can be done using a physical model on an adequately reduced scale or using an actual scale field test, see e.g., [12]. A failure caused by the soil sliding on the interface with a geogrid depends on the shear strength of the soil-geogrid interface, which can be determined using a large-scale direct shear test apparatus, e.g., [11,[13][14][15][16][17][18]. The reduction or increase in the shear strength properties of the soil-geogrid interface is given by the coefficient α, which represents the ratio of the shear strength of the soil-geogrid interface and the shear strength of the original unreinforced soil, e.g., [19].…”