In the railway industry, safety is an essential factor that has been modified by all societies and railroad managers. Against the background of increasing speed of rolling stock, risk factors such as cross wind and train stability have received more extensive attention. In this study, the porous wind barriers that are widely used in this industry have been surveyed. Also, to decrease the harmful effects of crosswind, the work attempts to find an optimum porous barrier design. This numerical simulation was based on a modern computational fluid dynamic in microscopic space model called the Lattice Boltzmann Method. Also, to find the optimum type of barrier design, the Multi-Objective Genetic Algorithm had been used. Two aspects of barrier design, including the porosity levels and distance between barriers, have been studied and, finally, a candidate design proposed for the barriers. It was found that porousity levels up to 15% have a positive effect in reducing the lift force coefficient, but beyond that it has a negative effect. On the other hand, increasing the porosity level leads to a decrease in the drag coefficient. The velocity vectors, velocity counter, vorticity, and turbulence intensity of the flow field around the model plotted for the candidate barrier.

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As the use of geogrid reinforced soil (GRS) walls increases, appropriate solutions should be considered to improve their performance. In recent years, wall construction in the multi-tiered configuration has improved both static and post-earthquake behavior, and become an appropriate approach to building high-reinforced soil walls. In addition to the above approach, treatment of the soil used as the wall backfill is also a suitable solution to enhance the wall performance. In this study, a combination of the two above concepts has been employed for better understanding the GRS wall behavior by developing a series of reduced-scale physical models. One-meter-high models in one- and multi-tiered fashion were tested backfilled with untreated and treated (by adding a combination of cement and polypropylene fibers) silty sand mixture. A comparison of the 1-g shaking table tests among wall models subjected to seismic waves indicated the influence of the treating solutions on the dynamic response of the walls. The findings suggest that use of the two proposed approaches in the GRS walls construction has a notable effect on the wall stability after construction and during an earthquake. It also improves the essential seismic parameters such as displacement and acceleration responses.

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Improving the characteristics of local low-strength soils at the construction site is one of the appropriate approaches to employ the soils as a backfill of geogrid reinforced soil (GRS) walls. In this study, the fiber-cement-treated sand-silt mixture was used as the backfill of walls. The post-earthquake performance of the walls was evaluated by applying the sinusoidal waves on 1-m high reduced-scale physical models and conducting a series of 1-g shaking table tests. A comparison of the wall models constructed with treated and untreated backfill indicated the advantages of geogrid-reinforced fiber-cement-treated soil walls subjected to strong ground motion. The results revealed the better behavior of the wall models backfilled with treated soil mixtures under dynamic loading. Such improved performance was more evident in (1) deformation responses, including the lateral displacement of wall facing, deformation mode, failure surfaces, and settlement of backfill surface and (2) acceleration response in different locations, including facing, reinforced, and retained zone of walls.