نشریه مهندسی عمران و محیط زیست دانشگاه تبریز
سال پنجاه و دوم شماره 4 (پیاپی 109، زمستان 1401)

Pipelines are used all around the world to transport fluids from one location to another. When these pipelines meet rivers, seas and oceans pipes are laid on the solid bed and it causes changes in the flow pattern around the pipes. In result of these changes, the shear stress of bed under pipelines and turbulence of current will be increased, and scour will occur under pipelines and the scour hole will form and develop. These holes cause damage and failure to the pipe due to the pipe weight. In case of failure of the pipe, irreparable damages will incur to the environment and there will be huge financial costs. Therefore, it is very important to study the scour depth and effective variables to reduce scour and prevent damages. Researchers have conducted experimental and numerical studies on scour phenomenon and have provided relations over the years.
In this research the effect of various factors on this phenomenon in steady current are investigated using Gaussian process regression (GPR) and support vector machine (SVM) and it is compared with the previous presented relations. To this end several laboratory data were used and after defining several non-dimensional parameters the performance of these methods was evaluated. The result of this research demonstrated that these methods are better than experimental relations and have promising outcomes. This study have shown that an SVM model with ℎ/D, D/d, Re and S0 variables in steady current have the best results. It is worth mentioning that ℎ and variables in steady current have the most significant effect on the scour below pipelines.

The abundance of saline water at ground level and their progression to freshwater and onshore sources, landfill leachate chemicals, or industrial plant effluents into the soil are factors that can change the amount and type of soil salinity and, as a result, their geotechnical properties (Ouhadi et al, 2015). Also, due to the size of the large dams reservoirs and the impossibility of changing the axis of the dams due to different constraints, it is possible that after the filling, the dam lake water will come into contact with the salt formations and may cause risks such as changing the geotechnical behavior of the clay core, after exploiting embankment dams. Therefore, due to the presence of contaminants, which is sometimes unavoidable, an understanding of basic mechanisms in modifying the physical and engineering properties of soils under the influence of chemicals or chemical salts is essential (Sen et al, 2017). In general, the concentration of ions affects the intermolecular forces of the soil (ie double-layer repulsion and van der Waals attraction) and the structure of the materials (Weimin et al, 2014; Zhu et al, 2015). As a result, such changes in soil structure alter its engineering properties (Yan and Chang, 2015). According to the extensive studies on the influence of pore fluid on clay soils, however, a comprehensive study from the microstructural perspective with regard to permeability coefficient changes on clay soils has not been conducted. The purpose of this study was to investigate the permeability coefficients and engineering properties of clay soils with a special attitude to clay core in the presence of sodium chloride solution salt as a pore fluid from a microstructural perspective..

The present work studies the capability of an aerobic biological (Ae-Bio) and a combined aerobic biological-advanced oxidation (Ae-Bio/UV-H2O2) process in the treatment of a toxic model wastewater composed of organic aromatic compounds, dyestuffs, and heavy metals. The coexistence of organics with heavy metals causes a high level of toxicity that raises the need for the successful adaptation of microorganisms to the wastewater before biological treatment processes. In each of the Ae-Bio and Ae-Bio/UV-H2O2 processes, the sludge was first adapted to the wastewater and then, the adapted sludge was used for the removal of COD and methylene blue in the wastewater.

Because testing on different materials often requires a lot of time and money, numerical simulation can be an acceptable method to avoid conducting several tests. One of the most effective methods to investigate the behavior of granular materials is discrete element method. This method, as a new approach, can simulate the behavior of material realistically, without implementing complex constitutive models (Wang et al, 2007; Shamsi and Mirghasemi, 2012; Tian et al, 2018). We know that the behavior of the particle assembly is influenced by the experimental test conditions, particle size distribution, particle shapes, etc. Previous researches show that particle shape has a significant effect on the mechanical behavior of granular soil (Tian et al, 2018). Therefore, to properly model the behavior of granules, it is better to simulate the particle shape as close to reality as possible. The main objective of this paper is to evaluate the effect of gradation and realistic particle shape on the mechanical behavior of granular soil in three dimensional discrete element method modeling in order to increase accuracy and precision of the simulation results. In this regard, in this study, irregular particles are modeled using a set of spheres that have different radii, overlap with each other and form a rigid object (clump) as shown in Fig. 1. Then, a series of consolidated drained triaxial compression tests have been performed on the specimens containing particles with various shapes. Finally, the results of the modeling were compared qualitatively with the experimental results.

The issue of energy crisis is considered as one of the main problems of this century. This has led to increased attention to renewable energy. In this regard, several solutions have been proposed to decrease the use of fuel and make more use of clean energy, including solar energy in various fields. On the other hand, in recent decades, most of the cities have expanded unprecedentedly. In many cases, physical expansion has resulted in high congestion, environmental pollution, and waste of time, fuel, and energy. Therefore, experts have proposed high-rise construction as one of the appropriate solutions for the development of cities (Cheng et al. 2006). While tall buildings, especially in large cities, due to shading, affect the amount of sunlight to their surroundings (Andreou, 2014; Jose et.al, 2011; Hayati and Sayadi, 2012). Therefore, high-rise construction should be done in a way that does not reduce the use of solar energy as much as possible. In addition to lowering the temperature of the building, the shade also makes it difficult for snow to melt naturally and rainwater to evaporate. With proper design of buildings in order to benefit from sunlight, the consumption of fossil fuels in buildings, especially in cold seasons and cold regions, is reduced to some extent. The effect of shading on the surrounding environment depends on various factors such as the height of the buildings and the distance between them. The taller a building is, the longer its shadow. In addition, the length of the shadow varies in different seasons; The longest shade occurs on the first day of winter. In this research, shading with real three-dimensional data of Adab 2 neighborhood of Sanandaj city, which includes several buildings, has been investigated. Sanandaj is the capital of Kurdistan Province in Iran, with a population of 412767 (in 1395). The selected study area is one of the areas where the rate of density and construction is relatively high and the issue of shading has not been given enough attention. In addition, the mountainous nature of the region and its cold climate have increased the need for sunlight, especially in cold seasons. This area has a latitude of 35 degrees and 17 minutes to 35 degrees and 18 minutes and a longitude of 46 degrees and 59 minutes to 47 degrees and 00 minutes east of the Greenwich meridian. Until the present study, no article on the practical use of GIS for shading in the country had been published in the relevant journals.

Human growing demand for energy and in recent decades for clean and renewable energy, leading to the development of wind farms inshore areas and have moved to offshore areas to achieve more production. Noticed that wind farms are a series of large, expensive and same structures, their foundations are important and it’s necessary to minimize the probability of failure all of them. Many wind turbines are founded on large piles called monopiles. In European countries particularly in offshore areas, dominant environmental loading on monopiles is the wave. But some of the pioneer countries in wind energy development, such as China, India and the United States are highly seismic areas. Following the occurrence of natural events of wave and earthquake in the sea at the same time, considering the behavior of monopiles under their combined effects are required. In this study, three-dimensional modeling of the soil-monopile system using Open Sees software by finite element analysis was carried out and the effect of wave load on seismic responses of monopile and its surrounding soil was investigated. The wave and earthquake loads applied simultaneously on the soil-monopile system. In the nonlinear behavior modeling for sandy soils, effects of the stiffness, permeability, dilation, and potential of soil compaction on system responses are included. Studies have shown that wave can be affected on the seismic responses of monopile significantly, in addition to amplification of monopile, rotation, shear force and bending moment, can change the location of maximum moment and shear in monopile.

Most studies show that some certain fiber can enhance to some extent both mechanical properties as well as ductility of lightweight concrete. On the other hand, due to high industrial potential as well as less damage to the environment, basalt fibers have gradually become an appropriate option to be used in the composite industries and thus is considered as a special competitor to other fibers (Ralegaonkar et al., 2018; Sadrmomtazi et al., 2018). In recent years, there has been a growing interest in the use of the intelligent inference and reasoning methods, including ANFIS and ANN to approximate nonlinear and complex concrete behaviors and predict its properties (Tesfamariam and Najjaran, 2007; Sadrmomtazi et al., 2013). Therefore, this study aimed to investigate mechanical properties of the lightweight structural concrete containing different amounts of basalt fibers (0, 0.1, 0.2, 0.3, 0.4, and 0.5%) as well as pozzolanic materials (silica fume and fly ash). In addition, the modified ANFIS was used as a robust method to predict results to evaluate the experimental results.

Today, new improvement methods to improve the geotechnical properties of soils are considered. Although a lot of improvement techniques are in use around the world, they have their own advantages and disadvantages. Chemical, physical, mechanical, biological and electrical techniques may be named as the common methods of soil improvement (Karol, 2003). Some of the methods, particularly those using cement and other toxic chemical grout, may cause environmental problems which limit their usage. In this regard biological improvement is an innovative method that uses microorganisms in the soil and biochemical reaction networks, the soil physical and mechanical properties are improved. In this research, mixed culture performance was studied against single culture of bacteria on physical strength properties of sandy soil, as the stabilization efficiency was evaluated in terms of the soil compressive strength, secant stiffness, and permeability with unconfined compression and falling head tests, respectively.

In the present study, the effect of ice-shedding simultaneously at the transmission line's span and the wind was investigated using numerical modeling, and its results are presented. The transmission line has five transmission towers and six power transmission spans related to the 400 kV transmission line of the Khoy-Urmia power plant. The transmission tower's weaknesses have been identified using this study's results, which can be considered in strengthening existing towers and the design of new transmission lines.

The reactivation of slip on pre-existing planes of weakness is of key interest to many geological phenomena, being implicit for instance in tectonic inversion theory and in the concept of stick slip behavior. The analysis of reactivation is crucial in engineering geology where rock masses must be below the critical stress level needed to initiate sliding and in reservoir geology for selecting safe hydrocarbon traps. It also constitutes a valuable tool in seismic hazard assessment as it provides a means of quantifying the slip potential on mapped or suspected faults in a known or inferred stress field.

The researchers tried to build gabion barriers by considering the materials around the dam. In this study, gabion barriers with applicability were used, in which trapezoidal barriers were made using metal mesh and these barriers were filled with sand grains with an average size of 0.5 cm. The reason for using these dimensions of aggregate was the presence of stones with dimensions of 0.5 meters in nature, and if the laboratory results are suitable, it is possible to use them in the implementation, while proper slope. According to the executive criteria, it was considered to build the sides of the barrier in order to evaluate the possibility of falling aggregates. In this design, an attempt has been made to investigate the effect of gabion barriers on the percentage reduction of flow head flow. To better understand their efficiency in different conditions, some important parameters such as concentration, inlet discharge, slope and height of barriers have been considered.

Progressive collapse studies generally assess the performance of the structure under gravity and blast loads, while earthquakes may also lead to the progressive collapse of a damaged structure. In this study, the progressive collapse response of concentrically braced dual systems with steel moment-resisting frames was assessed under seismic loads through pushover analysis using triangular and uniform lateral load patterns. Two different bracing types (X and inverted V braces) were considered, and their performances were compared under different lateral load patterns using the nonlinear static alternate path method recommended in the Unified Facilities Criteria (UFC) guideline. Eventually, the seismic progressive collapse resistance of models was compared to their progressive collapse response under gravity loads. These studies showed that models under the seismic progressive collapse loads satisfied UFC acceptance criteria and limited rehabilitation objective. The structures had better performance under seismic progressive collapse than models under gravity loads because of more resistance, ductility, suitable load redistribution, and more structural elements that participated in load redistribution. Furthermore, despite studies on progressive collapse under gravity loads, the dual system with X braces showed better progressive collapse performance (more resistance, residual reserve strength ratio and ductility) under seismic loads than the model with inverted V braces.

The main problem of water resources planning is the inappropriate allocation between different consumers. Water allocation planning is a complex, multi-variable, and multi-constraint problem, which requires advanced optimization methods to be solved. Classical optimization methods are facing some limitations such as being trapped in local optimum points, and difficulties in handling different variables. In this paper two of these methods including particle swarm optimization, PSO and multiobjective non-dominated sorting genetic algorithms, NGGAII were explored and their efficiency in optimization water reservoir operation problems is compared. Dealing with the necessary of multiobjective programing accuracy, two single objective models was developed separately using PSO to verify the NSGAII results.

Due to the difficulties of conducting tests, especially in weak rocks and the cost of these experiments, by examining the relationships between their mechanical and physical properties can be provided and reduce the cost of tests to identify mechanical properties (Minaeian and Ahangari, 2013; Azadan and Ahangari, 2014).     In this study, petrographic, physical and mechanical experiments on 62 cores of shale and marl of Gurpi Formation were conducted in Godar-Khosh dam site, west of Iran. Non-destructive tests were performed on cores according to the ISRM standard. Physical properties such as water absorption, density and porosity of the samples were determined according to the ISRM standard. Also, uniaxial compressive strength (UCS) test according to the ASTM standard D2938 (ASTM, 1986) was performed. For each sample, the modulus of dynamic elasticity (Ed) and the dynamic Poisson ratio were calculated (Goodman, 1989). Using statistical analysis, artificial neural network (ANN( and  support vector regression (SVR) with radial base kernel function, several relationships for estimating UCS, Es and shear wave velocity were presented. The root mean square error (RMSE), the mean absolute percentage error (MAPE) and the variance account for (VAF) were also used to evaluate the results.

With the development of urbanization and the increasing development of high-rise structures, there is a definitive need for excavation with higher depths. The important matter to be considered in such cases is providing stability of the excavation to prevent any probable risk in the urban environments. Because of excavation, the soil as a bearing system removed, and consequently, the equilibrium of in-situ stresses in the soil mass and the between-granular stresses are disrupted. If this stress change exceeded the tolerance limit of the soil, the soil would be unstable and, the excavation collapse will be inevitable. Hence, one of the aims of engineers in the assessment of excavation is the stability analysis so that the safety factor must always be above one. In addition to stability analysis and due to the effect of excavation on the surrounding area, deformation and settlement analyses are also necessary for the urban areas (Chen et al, 2020).

Cored earth dam is one of the most widely used dams, the construction of which is highly accepted among dam designers. The construction of these structures is very expensive, so optimizing the cost of design and construction of earth dams can be so helpful.Today, many optimization problems cannot be solved in practice with traditional optimization methods due to their large size and complexity. For this purpose, metaheuristic algorithms can be used, of which PSO is one. In the present study, the cross-sectional optimization of earth dams as the main part of the dam cost has been investigated by controlling the stability of slope in steady-state seepage condition.

The complex interactions between streameise flow and curvature- induced secondary flow in bends, bed morphology cause erosion near the outer bank, and deposition near the inner bank, that it can endanger the outer bank’s stability and also reduce the navigable width of the rivers. There are several techniques to protect the outer bank, reduce adverse impacts and control bed erosion in bends. Methods used in most parts of the world include submerged groynes, spur dikes, and bandal-like structures. But, meny these Methods have the disadvantage of being fixed constructions on the bed river that caused a threat for navigation. This paper describes a new way that consists in changes the bed morphology with provoking changes in the flow pattern. Dugue, et al. (2011, 2012) studied morph dynamic bends rivers with the Air-bubble screen method. Their results reveal that the air bubble screen is able to modify the flow pattern by shifting the maximum scouring from the outer bank towards the center of the flume and does not endanger its stability anymore. Dugue et al, 2013 studied scour reduction at a 193° bend by an air-bubble screen method. Velocity pattern at 70° bend showed that the bubble-induced flow pattern overcame the secondary flow induced by the outer bank while decreasing the morphology slope. It also showed 50 percent reduction in the maximum scour depth. Shukry (1949) is one of the first researchers in the study of erosion of the outer bank of rivers in a canal with a 180- degree bend with various proportions of the rivers radius to its width. There have been very few investigations about air bubble screen in 90 bend, therefor  in this study the effect of the air bubble screen on flow pattern and Secondary flow strength  and bed shear stress in 90 degree bend under Froude numbers 0.45 is examine.