Abstract
Geosynthetic-reinforced soil structures are mostly used to retain subgrade slope of highway and railway. For the design and performance analyses of geosynthetic-reinforced soil structures under repeated loading, such as those induced by compaction, traffic and earthquakes, the understanding of cyclic soil–geosynthetic interface behaviour is of great interest. Nevertheless, experimental data concerning this type of behaviour are very scarce. A laboratory study was carried out and is described in this paper. This paper presents the behaviour of an interface between a coarse-grained soil and a geogrid under cyclic loading conditions. A large-scale direct shear test device able to perform displacement-controlled cyclic tests was used. The results obtained are presented and discussed, especially the effects of the displacement amplitude and normal stress on the shear stiffness and damping ratio are investigated. The dynamic response parameters of the soil-geosynthetic interface are greatly affected by the number of cycles, and the variations in the two parameters with the number of cycles are related to the normal stress and the shear displacement amplitude. when at large displacements, the damping ratio decreases first and then stabilizes with the number of cycles. However, at small displacement, the shear stiffness and damping ratio are all decrease somewhat at the initial stage of cyclic shearing. As the experimental materials used in this study are relatively single, and further experimental research should be carried out in the future. The shear parameters of interface in this study can provide reference for the design of reinforced soil structure.
Highlights
With regard to highway and railway subgrade engineering, geosynthetics are often used to enhance the stability of subgrade slopes
The positive loading starts from the shear displacement of 0 mm, and the shear stress increases with shear displacement and reaches the peak value at the same time when the displacement is maximum
The greater the displacement amplitudes are, the greater the load variation during the unloading stage. This is because the greater the displacement amplitude is, the greater the damage to the soil-geosynthetic interface, especially the damage caused by the breaking of the geogrid ribs
Summary
With regard to highway and railway subgrade engineering, geosynthetics are often used to enhance the stability of subgrade slopes. For the interaction between geosynthetics and soil under a dynamic load, Zhang et al, [15] developed a large-scale 3D testing machine for the soil-structure interface that was adopted to study the cyclic mechanical properties of the contact surface. Liu et al, [20] studied the impacts of different geotechnical materials and cyclic loading on the interface shear stiffness and damping ratio by adopting a large-scale multifunctional interface shear apparatus, but the number of cycles was only 10, which made it difficult to fully reflect the actual loading condition of the reinforced soil structure. The large amplitude cyclic shear test and small amplitude cyclic shear test are carried out, and the variations in the shear stiffness and damping ratio under different dynamic loads for geogrids against coarse-grained soil interfaces has been obtained, which can provide effective parameters for the stability analysis of reinforced soil structure
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