جستجوی مقالات مرتبط با کلیدواژه « quicksand » در نشریات گروه « عمران »

One of the inevitable necessities for the development of the rail transport network is to pass through desert and sandy areas. At the same time, desert railways increase maintenance and repair costs, reduce speed and block the line during operation, and even cause the train to derail. So far, various solutions have been proposed to deal with quicksand in desert railways. One of the newly developed methods is the hump slab track, which seeks to control and pass the amount of incoming sand from the railway track. In this system, the ballast material is removed and the height of rails is raised by means of concrete supports known as humps. As a result, channels for the passage of sands under the rails are created. The geometry of the hump should be such that, in addition to favorable aerodynamic conditions, it provides maximum free space for sand to pass through. In this research, with the aim of optimizing the geometry of the hump, different sections for the hump have been investigated and then two main sections including oval and rectangle-semicircle with two different heights have been evaluated. Simulations have been carried out in the platform of computational fluid dynamics and in Ansys Fluent software. Two-phase solid-gas flow including a sand flood and wind flow has been passed through the models and the amount of sand volume fraction has been compared. The results show that the rectangular-semi-circular geometric section (height of 20 cm) shows more favorable results against the influx of quicksand.

In two decades, the roads of the roads in the desert areas of the desert have also been changed. Fiber-reinforced soil behavior modification studies have been performed by compaction, uniaxial compressive strength, and California load-bearing ratios. In this research, studies were performed on soil stabilization of constructing roads in sandy loam soils using cellulose nanofibers. The aim of this study was to stabilize the cracked pavement bed and strengthen it by adding nanocellulose to the soil. Physical and mechanical tests were performed to find the type of soil in the area and the effectiveness of nanocellulose. Samples in these experiments were combined with 0.5, 1 and 1.5% nanocellulose, The results obtained from the experiments showed that the addition of nanocellulose increased the liquid and plastisite between 21 to 27% and 60 to 65% and decreased the plastisite index between 25 to 40%, respectively. Optimal moisture and dry specific gravity increase and decrease, respectively. The uniaxial strength of the samples increased between 30 and 85% and the maximum CBR number up to 12 times., and the soil strength class in all samples was changed to "very good" subgrade for use in pavement. The rupture zone energy results also show that the increase in nanocellulose has a positive effect on the modified specimens and delays the occurrence of rupture cracks due to loading and volumetric changes. The response Surface statistical method was also used to predict objective variables.