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Railway transportation in Iraq is irreplaceable for its significant role in economic growth. Due to inadequate maintenance and upgrading of the railroad, the Iraqi transportation system has deformed and poor-quality rails. The ballasted track is the traditional railway system where the ballast and sub-ballast layers provide structural support against the high dynamic stresses transmitted from moving trains. This paper attempts to study the effect of geotextile reinforcement on railway-ballasted track layers using the Abaqus program to examine the behavior of railroads' railway-ballasted trucks of varying thicknesses reinforced with geotextile. The study used the finite element method and adopted simulation to investigate the behavior of the railways. The sub-ballast thicknesses used are 150, 200, 250, 300, 350, and 400 mm, with 200 mm ballast thickness and 4 m subgrade thickness. The findings revealed that a 50 mm increase in subballast thickness resulted in a 7.2% reduction in deformation. The findings show that utilizing geotextile atop the ballast layer is equivalent to increasing the sub-ballast layer's thickness by around 3.57 cm to reduce track distortion. The result showed that using geotextile would reduce model settlement with a range between (38-18) percent for total model settlement for the different models that have been tested. In addition, using geotextile under the ballast layer is more effective in reducing model settlement if there is an economical restraint to use only one reinforcement layer. [ABSTRACT FROM AUTHOR]

The essential nature of dispersive clays was first noticed by U.S. Dams' soil scientists and agricultural engineers. Highway embankments and natural formations of high sodium dispersive clay were recorded as severely damaged by internal (tunnel) erosion of water flowing in the form of concentrated leaks within cracks. These dispersive clays, which cannot be differentiated from ordinary erosion-resistant clays by the routine civil engineering tests, erode rapidly in slow-moving (or even quiet) water by individual colloidal particles going into suspension. In Iraq, few studies were interested in such types of soils; that's why the present study takes into consideration dispersion of Baghdad clayey soil brought from three different Zones in Baghdad; the first soil is brought from Al. Kazaliyah district Zone (A), This Soil is classified as (CH) according to the Unified Soil Classification System (USCS). The second soil is brought from Al. Qadisiya District Zone (B) is classified as (CH), while the third Soil is Al. Dora region Zone (C) is classified as (CL). The conventional testing and interpretation are found to be inapplicable to analyze and identify the Dispersion soils due to the existence of Na+. The effect of water content was studied in two different tests for each soil; the pinhole test and soil retention test. The behavior of dispersive soil is not affected by water content, but water content may change the time to failure. This fact gives a good and new indicator of the maximum time to failure. [ABSTRACT FROM AUTHOR]

The major purpose of the pavement structure is to reduce stresses in the subgrades so that there is little or no deformation in the subgrade. Therefore, the more the subgrade is resistant to deformation, the thinner the pavement will be, thus reduction in the construction cost of the road. Finite Element techniques can be effectively applied to simulate different pavement problems that could not be modeled using the simpler multilayer elastic theory. Thus, finite element Abaqus 6.14-1 program is used in this study. The laboratory tests are carried out on both the natural and stabilized soil samples that used as subgrade layer to determine the properties of subgrade that will be used as inputs for the finite element Abaqus program. The natural samples tested with three percentages of moisture contents (11.5%, 13.5%, and 15.5%). Different types of stabilizers are used in this study in form of mixture of two types of stabilizers. So, mixture of lime-kaolin (3%, 4%), mixture of silica fume-Poly Vinyl Alcohol (2%, 2%), mixture of Rice Husk Ash-Poly Vinyl Alcohol (3%, 2%), and 2% of silica fume are used as stabilizers. The pavement application by Abaqus program indicating that, the characteristics of subgrade layer have a big influence on the vertical deformation of whole pavement. The combination of (3% of Rice Husk Ash and 2% of Poly Vinyl Alcohol) as a stabilizer to the subgrade layer reduces the deformation about (9.5 %). While the addition of (3% of Lime and 4% of Kaolin) led to regard the deformation about (7.8%). [ABSTRACT FROM AUTHOR]