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

Abstract

The paper deals with the laboratory testing of coarse-grained soils that are reinforced using a geogrid. The shear strength properties were determined using a large-scale direct shear test apparatus. The tests were executed on original as well as on reinforced soil, when the geogrid was placed on a sliding surface, which permitted determining the shear strength properties of the soil-geogrid interface. The aim of the tests was to determine the interface shear strength coefficient α, which represents the ratio of the shear strength of the soil-geogrid interface to the unreinforced soil. The tests were executed on 3 samples of coarse-grained materials, i.e., poorly graded sand, poorly graded fine gravel and poorly graded medium gravel. Two types of geogrids were tested, i.e., a woven polyester geogrid and a stiff polypropylene geogrid. The results of the laboratory tests on the medium gravel showed that the reduction coefficient α reached higher values in the case of the stiff polypropylene geogrid. In the cases of the fine gravel and sand, the values of the interface coefficient α were similar to each other. The shear strength of the interface was reduced or was similar to the shear strength of unreinforced soil in a peak shear stress state, but significantly increased with horizontal deformations, especially for the fine gravel and sand. The largest value of the coefficient α was measured in the critical shear stress state. Based on the results of the testing, a correlation which allows for determining the optimal grain size distribution was obtained.

Shear Strength Properties of Coarse-Grained Soils Determined Using Large-Size Direct Shear Test

“…The determination of the shear strength properties is summarized in section 5.3 for all the samples tested. presented by the authors [32]. The shear strength at point A was reached for a horizontal movement of about 0.8 -1.0 mm and the peak shear strength for a horizontal movement of about 4 -6 mm.…”

Investigation of Cement and Fly Ash on the Improvement of Fine Sand Soil

“…Normal stresses applied on top of the soil samples were 54.5 kPa, 109 kPa and 218 kPa, respectively. The horizontal load was applied with a speed of 0.5 mm/min [24,25].…”

Analysis of Geogrid Reinforced Structures with a Passive Facing System Using Different Computational Methods

“…Drusa et al [23] stated that R inter parameter could be directly set in the soil, based on practical experiences, see also [20], and a value of 0.9 for crushed stone material can be used. Based on the results of the laboratory tests presented by Stacho et al [24], the R inter parameter for the material of analysed embankments (Tables 3 and 4) exceed the value of 1.0; so in numerical models, R inter = 1.0 was used. Two road embankments supported by wrapped GRS with a passive facing system were modelled and analysed.…”