The irrecoverable deformations in the substructure layers are detrimental to the track stability and demand frequent maintenance. With an escalation in axle load and traffic volume, the frequency of maintenance operations has remarkably increased. Consequently, there is an inevitable need to predict the long-term behavior of the track substructure layers. This article presents a methodology to evaluate the recoverable and irrecoverable responses of the substructure layers under the train-induced repetitive loads. The present method utilizes an integrated approach combining track loading, resiliency, and settlement models. The track substructure layers are simulated as lumped masses that are connected by springs and dashpots. The method is successfully validated against the field investigation data reported in the literature. A parametric study is conducted to investigate the influence of substructure layer properties on the track response. The results reveal that the response of each track layer is significantly influenced by the neighboring layer properties and the incorporation of multilayered track structure enables more accurate prediction of track behavior. The present analytical approach is simple, computationally efficient and may assist the practicing engineers in the safer design of the ballasted track.

Soil nailing is a popular in situ reinforcement technique that is widely used to stabilize unstable slopes and vertical faces of excavations and tunnels. The pullout capacity of soil nails is a governing design parameter for the soil-nailing technique. Therefore, the determination of accurate pullout capacity is necessary to ensure adequate internal stability of the stabilized structures. The article presents a laboratory investigation on the pullout force–displacement behavior of the soil nails installed in a dry, cohesionless medium. The study describes the effects of surface roughness, surcharge pressure, and relative density on the pullout response of soil nails. The results show that with an increase in the roughness, there was an increase of more than twofold in the mobilized maximum pullout resistance of the soil nails. Furthermore, the relative density was found to have a significant influence on the pullout capacity and the mobilized peak interface friction angle of the soil nails. The pullout force–displacement behavior of the smooth surface soil nail was found to be elastic–perfectly plastic in nature, whereas a strain-softening behavior was observed for the soil nails with a rough surface. The experimental data were used to formulate an empirical model (substantiated by the previously published data) that can predict the peak and residual shear strength of the nail–soil interface at different combinations of surface roughness and surcharge pressure. The proposed empirical model was then incorporated into the existing constitutive models to reproduce the observed (experimentally) pre and postpeak pullout force–displacement response of the soil nails. The simulated results are in good agreement with the experimental observations.

The surface texture of the interface material plays a significant role in the shear behaviour of soil–continuum interface. This study investigates the influence of surface texture of steel on the shear behaviour of sand–steel interface using different types of steel counterfaces with distinct texturing patterns. The patterns include concentric circular asperities, square-tiled surfaces with equally spaced individual asperities and ruled ribbed asperities oriented parallel, perpendicular and at an angle to the shear direction. The results show that the texturing pattern of the steel counterface significantly affects the shear strength of the sand–steel interface. The peak and residual interface friction angles for the sand–steel interfaces with different texturing patterns (with identical asperity height and spacing) varied from 26·6° to 37·5° and 14·2° to 28·7°, respectively. Moreover, the surface with ruled ribs/asperities inclined at right angle to the shear direction shows the maximum interface shear strength among all the texturing patterns tested. The findings presented herein are imperative for a realistic assessment of the performance of geotechnical structures involving soil–steel interaction.

Three-dimensional cellular geoinclusions (e.g., geocells, scrap tires) offer all-around confinement to the granular infill materials, thus improving their strength and stiffness. The accurate evaluation of extra confinement offered by these geoinclusions is essential for predicting their performance in the field. The existing models to evaluate the additional confinement are based on either a plane-strain or axisymmetric stress state. However, these geoinclusions are more likely to be subjected to the three-dimensional stresses in actual practice. This note proposes a semi-empirical model to evaluate the additional confinement provided by cellular geoinclusions under the three-dimensional stress state. The proposed model is successfully validated against the experimental data. A parametric study is conducted to investigate the influence of input parameters on additional confinement. Results reveal that the simplification of the three-dimensional stress state into axisymmetric or plane-strain condition has resulted in inaccurate and unreliable results. The extra confinement offered by the geoinclusion shows substantial variation along the intermediate and minor principal stress directions depending on the intermediate principal stress, infill soil, and geoinclusion properties. The magnitude of additional confinement increases with an increase in the geoinclusion modulus. The findings are crucial for accurate assessment of the in situ performance of three-dimensional cellular geoinclusions.