نشریه مهندسی عمران فردوسی
سال سی و پنجم شماره 2 (تابستان 1401)

In this research work, the relationship between suction and swelling potential and swelling pressure of an expansive soil with different chemical pore fluid qualities was investigated through experimental tests. Different soils were prepared with different chemical qualities of pore fluid (distilled water, sodium chloride, and calcium chloride solutions with concentration of 250 g/l). The samples were made by the static compaction method for testing. Soil-Water characteristic curves were determined by the filter paper method for each prepared soil sample. By performing the swelling tests, the amount of free swelling and swelling pressure for different water content were obtained for each sample with different pore fluid. By using the Soil-Water characteristic curve of each sample, the equivalent suction was obtained for each water content. Then the curve of variations of free swelling and swelling pressure versus suction were obtained for each pore fluid. The results showed that the pore fluid with different qualities causes different Soil-Water characteristic curves. On the other hand, comparing the results showed that, at a given suction the swelling potential and swelling pressure of the samples with NaCl solution as a pore fluid was more than the samples with the pore of distilled water or CaCl2 solution. In addition, the SEM results revealed that the soil structure is dependent on the used pore fluid quality. Also, for a specific pore fluid, the soil structure is not the same at the beginning and end of the test.

Identifying the parameters affecting traffic flow density can be effective for decisions makers and policies for investment and prioritization of executive plans and projects. In this research, the effects of vehicle specifications on traffic density in the highway network of Tehran have been identified. For this purpose, information of Hemat highway has been collected and modeled. Geometric details and movement characteristics of cars can affect the quality of traffic flow. The present study is an objective research type and is survey research in terms of data collection. This issue is more crucial in highway and arterial crossings where other parameters such as delays and stops due to intersections and interferences are less. The method of research is quantitative and statistical models have been used to analyze the data. According to the results of the study, the length of vehicle, travel time, vehicle speed and volume of vehicles had the greatest impact on traffic density.

In predicting the behavior of geotechnical structures that are constructed on unsaturated soils, knowing the geomechanical properties, especially effective stress, is of particular importance. The effect of suction in unsaturated soils changes the volumetric and shear behavior of soil. Therefore, in determining the shear strength in unsaturated soils, the effective stress parameter (χ) plays an essential role as a function of suction. Determining this parameter requires a lot of time and money that is spent on laboratory tests. The purpose of this study is to evaluate several intelligent methods for creating models that indirectly accurately estimate parameter (χ). For this purpose, 120 data (which are the results of thriaxial, shear, pressure plate and filter paper tests) and intelligent methods of random forest, support vector machine and k-nearest neighbor were used in WEKA intelligent software. The results show that the models developed by the three intelligent methods of random forest, support vector machine and k-nearest neighbor, have excellent performance and accuracy. But the random forest model is better than the other two models in evaluating the test data with R2 = 0.918 and RMSE = 0.079. In addition, in this study, sensitivity analysis was performed to determine the importance of the parameters affecting parameter (χ). Among the input parameters in modeling, it was found that the volume water content parameter (θ_r/θ_s ) has the greatest effect on parameter (χ).

The Shatta al-Arab River is approximately 200 km long and is formed by the confluence of the Tigris and Euphrates rivers in the city of al-Qarna, 74 km northwest of the port city of Basra in southern Iraq. The river is affected by climate change and frequent rains, it shows the risk of flooding and overflowing at the riverside. The Shatta al-Arab River Basin in the city of Basra has been faced with floods and devastating consequences. The purpose of this study is to evaluate and analyze the spatial risk of river overflow of the Shatta al-Arab River in the city of Basra, Iraq, using the Geospatial Information System (GIS). GIS was used to estimate and evaluate the location and zoning of the Shatt al-Arab floodplain in Basra using the available data. By identifying the types of land uses around the river, provided a detailed analysis of how they are distributed in different risk areas. The results show that the agricultural landuse due to its large area is more at risk than other uses. The results of this study can have a significant impact on preventing irreparable flood damage in this area.

Hydraulic conductivity is the most important variable in groundwater flow equations that is applied in estimating water flow velocity, predicting pollutants transport, solving geotechnical problems, and determining groundwater resource management plans. In this research, an attempt has been made to estimate the amount of hydraulic conductivity in a part of Assaluyeh Aquifer using the empirical equations. For this purpose, the results of particle size distribution provided for 20 alluvial samples have been used. The values of hydraulic conductivity obtained from the empirical methods vary between 0.1 to 4.3 cm/day, which is in the range of common hydraulic conductivity of fine grained soil. Due to the significant amount of sand and gravel in the samples, it seems that the calculated hydraulic conductivity are somewhat less than its actual value. The results of this study show that according to the existing conditions and limitations for the use of each of empirical relations, the calculated hydraulic conductivity may cover a wide range of variations. Therefore, it is recommended to perform pumping test to verify the calculated hydraulic conductivity.

Due to population growth and the increasing number of vehicles on rural roads, traffic accidents have become one of the most important problems in the transportation system. Heavy vehicles have a great impact on the economic progress of developing countries such as Iran. Due to the possibility of trade with the Caspian littoral countries and the existence of agricultural lands, rural roads in Guilan province experience a large volume of heavy vehicles. This study aims to investigate the factors that influence the severity of heavy vehicle crashes on rural roads using Kolmogorov-Smirnov and Friedman tests as well as a logit regression model. The results show that the presence of curves in road geometry, head-on collisions, off-peak crashes (1 AM to 6 AM), and peak crashes (7 PM-midnight), familiar drivers, and agricultural vehicles are associated with more severe injuries. Furthermore, motorcyclists are the most vulnerable road users in crashes involving heavy vehicles. On the other hand, some factors such as the presence of road median, side-swipe collision type, and clear weather reduce the severity of crashes.