نشریه مهندسی عمران مدرس
سال بیستم شماره 2 (خرداد و تیر 1399)

Usually, the produced leachate at landfills contains several types of heavy metal contaminants. These heavy metal contaminants have been applied to the soil liner of landfills in combination with each other or sequentially. Accordingly, heavy metals are in competition with each other for sorption and retention by soil liner of landfills. In general, clayey soils, such as bentonite that is commonly used to prevent contaminant transportation in landfills, have different sorption preferential, which is called selectivity. On the other hand, there is a probability of changing the pH of soil liners of landfills by acidic conditions of leachates. This change in pH, affects the retention mechanisms of heavy metals by clay soils due to the change in physical and geo-environmental properties of the soil. In spite of several researches which have been conducted on interaction mechanism of bentonite and heavy metals, there is a lack of study on selectivity of heavy metals and bentonite in single and composite systems. The main objective of this research is to study and to compare the effect of initial pH of bentonite on its selectivity order in single species and composite species of heavy metals. To achieve this objective, the pH of the bentonite samples was changed and was stabilized, at different pHs by addition of concentrated hydrochloric acid to the bentonite suspension. Then, the interaction of these bentonite samples, which had different initial pHs, with lead and zinc in single and composite systems has been studied. This interaction has been investigated from theoretical and experimental point of view. The research results show that, the selectivity of heavy metals by bentonite samples with acidic pH of 2 and 4 in single and composite systems are relatively similar. However, the selectivity percent by natural bentonite (pH:10.5) in composite system relative to the single system was increased. Furthermore, the quantity of retention of lead and zinc in bentonite sample with initial pH of 2 in comparison with retention capability of natural bentonite (initial pH of 10.5) has decreased 60 and 70 percent, respectively. The noticeable reduction in heavy metal retention by acidic bentonite provides a major challenge in acceptance of bentonite as an appropriate material for contaminant adsorption. As the pH of bentonite decreases to acidic conditions, the impact of selectivity adsorption of bentonite at the presence of lead and zinc ions decreases which means a better correspondence with double layer theory. Furthermore, the pattern of lead and zinc retention by bentonite samples with initial pH of 4 and 10.5 in conjunction with the peak intensity variations of montmorillonite in bentonite XRD pattern in those initial pHs show that the largest retention capability of bentonite for zinc retention occurs at 100 cmol/kg-soil. However, the largest retention capability of bentonite for lead retention occurs at 200 cmol/kg-soil. Finally, based on the results of this research, from microstructural point of view the lead ions due to the more interaction with clay double layer have more influence upon microstructural properties of montmorillonite. Such an interaction may affect the extent of contaminant transport in soil.

Structural health monitoring is essential to predict problems and maintain structure integrity which can be effective in prolonging the structure lifetime. The accumulation of failure in the structures causes a severe structural fracture; therefore, the development of damage detection methods for structural fracture is one of the most important points in maintaining the integrity and safety of the structures. In this paper, damage identification in functionally graded (FG) porous circular plates based on modal data and vibration analysis on elastic foundation is carried out. The vibration analysis process is performed based on first-order shear deformation theory and analytical method. Circular plates are widely used in the industry, for example in bower, balconies, screens, halls and swimming pool ceilings. Functionally graded materials are a new type of composite materials and may be characterized by the variation in composition and structure gradually over volume, resulting in desired changes in the characteristics of the material. The porous materials are lightweight, flexible and resistant to tiny cracks, these materials have two phases; their first phase is solid and the second phase is liquid or gas. The proposed method is achieved using modal analysis information extracted from a mathematical code in MAPLE. Based on this method, the plate can be examined with different boundary conditions including clamped, free and simply supported. Power series method has been used to solve the governing equations of circular plate. For the first part of the circular plate, the power series expands around the zero point and for other parts of the plate, the power series expands around the outer radius of its own part. In this study, first of all, the governing equations of circular plates were extracted based on first-order shear deformation theory and displacement functions. Two types of porosity have been used for applying porosity to the plate. Thereafter, the continuity conditions of displacement which generally include 6 items have been applied: continuity of in-plane displacement of the middle layer, continuity of rotation of the transverse surface, continuity of displacement of the plate, continuity of in-plane force, continuity of bending torque and continuity of transverse shear force per unit length. Furthermore, stress resultants in the points of connection have been applied which includes 3 items: in-plane force, bending torque and transverse shear force per unit length. The matrix determinant that is based on boundary and continuity conditions has been calculated to find the natural frequencies of the plate. After that, based on the Newton-Raphson method which is a numerical method for determining the root of a function, the initial natural frequencies of the circular plate were obtained and their modal shapes were plotted. At the end of the process, when the natural frequencies are determined, the unknowns were calculated. To prove the accuracy and efficiency of the proposed method, the natural frequencies obtained from this method were compared with the results presented in other papers. The comparisons have shown that the results obtained through this study had a good agreement with those of other ones and the proposed method could accurately show the damage location.

Dissipating high kinetic energy of supercritical flows for the purpose of protecting downstream structures has always been a concern of hydraulic structure engineers. One of the approaches to tackle this problem is the utilization of hydraulic jump phenomena in which a great amount of kinetic energy is dissipated through turbulence which is more pronounce in roller part and conversion to potential energy in term of depth increase at downstream end and turbulence. A hydraulic jump may occur in prismatic or non-prismatic, converged or diverged and horizontal or inclined channels. However, there are oblique shock waves initiating at the start of a contracted channel, interact with each other and sidewalls and may create a complex flow pattern which is detrimental to the channel itself and downstream facilities. The present research aims at studying hydraulic jumps taken place in a converging inclined channel. The main parameters of a hydraulic jump such as its location, initial depth, ratio of conjugate depths, jump length and energy dissipation are studied for various inclination and convergence ratios and inflow conditions.

The experiments were conducted in a channel with different bed slopes of 0, 5, 10, and 15 percent, and convergence angles of 3.66 and 5.4 degrees. The end sills of 0.75 to 11 cm high were installed at the end, depending on the bed slope, to fix the jump location in the channel. The entrance was set carefully to produce the least disturbance due to sharp edges and protruding elements appeared in the flow; hence, a symmetric hydraulic jump may be observed all over a cross section. In order to double-check the accuracy of measurements, clips of various hydraulic jump were shot through sidewalls, converted into the images and digitized using GrapherTM.
Discussion and

The length of a hydraulic jump, was mainly a function of bed slope, such that by increasing the slope to 15%, the increase in the jump length was about 37.5% in average. Specifying a unique initial depth in a converging channel was challenging. There were oblique waves originated from the concave corners and coincided at the center line of the channel. In cases where the hydraulic jump occurred before the coincidence of the oblique waves there were three different depths at the start of the jump. In this work, the centerline depth was selected as depth of reference in the development of equations. By enhancing the bed slope, the mean initial depth decreased and the conjugate depth ratio increased. The energy dissipation increased by both the bed slope and convergence ratio. However, the effect of bed slope was more significant such that the average growth of dissipation in a horizontal bed was about 30% compared to a sloping bed. By increase of initial Froude number the difference between energy dissipation in various bed slopes approached to that of a horizontal bed. Using regression models, empirical relationships were developed for the estimation of length, conjugate depths ratio and energy dissipation of a hydraulic jump in an inclined converging channel.

Poorly graded sandy soil could cause numerous geotechnical problems in large areas across the world. Weak soils have insufficient bearing capacity and this may be the cause of many issues in roads infrastructure, embankments, buildings foundation, and other geotechnical projects. Stabilizing the soil by chemical stabilizers like ordinary Portland cement (OPC) is one of the most conventional methods for enhancing the engineering proprieties of soil, usually by different percentages of binder/soil ratio. Some environmental and economical issues of utilizing OPC as binder are the serious concern of researches during few decades. Alkali-activated materials (AAM), with lower destructive impact on environment and more economical profits, have been one of the attractive materials as a new generation of binders recently. These materials can be utilize in different geotechnical applications such as: soil stabilizing, different kinds of mixing method, and grouting. The current study has aimed to evaluate the mechanical and durability properties of stabilized sandy soil by AAM, the used slag for AAM binder is Ground Granulated Blast furnace Slag (GGBS) and the slag is activated by different kinds of novel alkali activators. The activators are combination of Na2SiO3 and NaOH, Na2CO3 and Ca(OH)2, and Na2SO4 and Ca(OH)2; namely, Ac1, Ac2, and Ac3, respectively. In order to evaluate mechanical properties of stabilized soil samples, unconfined compressive strength (UCS) test, and to investigate the durability properties of stabilized soil samples, freezing-thawing cycles are applied to specimens. Additionally, scanning electron microscopy (SEM) test are implemented on Ac2- and Ac3-based stabilized samples to investigate the morphological aspects of stabilized soil. Studied parameters of this study are the effect of curing time on mechanical behavior of stabilized soil samples, and the effect of types of activator on mechanical and durability properties (volume changes and soil-cement losses) of stabilized soil samples. Curing time of 14, 28, and 90 days are considered for UCS test, and 28 days are considered for freezing-thawing cycles durability test. The amount of binder for soil stabilization is considered in a constant value of 5 wt.% of dry soil for UCS and freezing-thawing tests. The 90-day UCS value for OPC-based stabilized sample is 0.75 MPa, for As1-based stabilized sample is 2.63 MPa, for As2-based stabilized sample is 2.28 MPa, and for As3-based stabilized sample is 4.5 MPa. As seen, AAM-based stabilized soil samples show greater UCS value in the same binder/soil ratio and curing time. As3 showed the most effective activator with higher UCS value as a soil stabilizer. In the test of freezing-thawing, except As2-based stabilized sample, other samples survived all 12 cycles. As2-based soil stabilized sample only survived 7 cycles of freezing and thawing. The most amount of volume changes for OPC-based stabilized soil is 12.82% for 12 cycles, while this amount is 6.65% for As2-based stabilized soil for 7 cycles. As1- and As3-based stabilized soil have showed fairly stable volume changes; i.e. with the most amounts of volume changes of 5.93% and 4.17% for 12 cycles. This results show AAM-based stabilized samples are more soundness than OPC-based stabilized samples and are more stable during volume changes.

The RCC construction method is one of the alternative methods in constructing concrete and earth dams. RCC is a kind of concrete which is pressed with roller, and after being compacted with roller, it is changed to a concrete like normal concrete .Primarily, using RCC in dam construction was developed to obtain the concrete structural properties and a construction method similar to earth dams. In RCC mix design, compressibility, non-segregation, maintaining the consistency of the fresh concrete, limiting the permeability, and achieving the proper bonding among the layers is required for efficiency .A qualitatively and quantitatively wide range of materials are used for constructing RCC mixtures in different dam projects. Therefore،Primarily the RCC aimed to obtain the conventional concrete properties and the construction procedure similar to earth dams. The quality and accessibility to materials to produce RCC should satisfy the structural and durability requirements. Therefore, the proper ratio of roller compacted concrete Mixture is an important step in achieving an economical and durable concrete.  This study aims to investigate the effects of various factors on the dam RCC Mixture Design (a case study of Javeh dam in the West of Iran), which optimum Mixture Design was developed as a laboratory research while observing all technical requirements and finally it was conducted as a test pad application. Javeh Reservoir Dam is located in a distance of 40 km southwest of Sanandaj, Kurdistan and 6 km from the downstream of Gaveh Roud and Qeshlaq River intersection. The dam is made of RCC. The properties of RCC in fresh and hardened conditions are of particular importance. Technical and economic advantages of RCC dams depend on the suitability of the mix design. Therefore, by an appropriate mix design, we can investigate the effect of RCC composite materials on the strength properties of RCC in terms of compressive strength, efficiency and non-separation characteristics of aggregates and their ratios in an optimal mix design. RCC must have sufficient efficiency to achieve the desired density according to the method and facilities. The efficiency of the new mix of RCC is entirely influenced by the amount of paste in the RCC mix. The paste contains the materials finer than #200 sieve including cement, pozzolan, water, filler of the aggregates and air bubbles. From the results, the total cementitious materials used in the optimum laboratory Mixture Design is 125 kg/m3. In addition, the ratio of Paste to mortar was about 5% higher than the minimum recommended in the RCC instruction given in the manual of the US Army Corps of Engineers. The compressive strength of roller concrete is affected by factors such as the amount of aggregates, the quality of fine grains, the quality of cement materials, grade density and content of mixed moisture. Considering that artificial neural networks are among the modeling methods that have shown great power to adapt to engineering problems, the models for predicting the compressive strength of this type of 180-day concrete is discussed based on the actual results from laboratory Mixture Design by neural networks modeling. The values of correlation coefficients in each of the models made in this study were close to the value of 1, which indicates the appropriate accuracy of the models.

One of the most concerns about design and maintenance of structures in civil engineering is the safety of structures in the events of natural disasters, including earthquakes, which requires adequate resistance and providing expected performance of structures. Different factors can have an impact on the occurrence of damage and the damage content in structures and, consequently, the loss of economic assets as well as human health and life safety during earthquakes. Normally, high alkaline property of concrete, PH about 13, forms a protective oxide layer on the reinforcement steel surface. The Carbon dioxide in the atmosphere or the chloride ion in the concrete environment especially in the coastal zone, along with the moisture and the oxygen can penetrate through the concrete pores and micro-cracks and can reach the rebar surface. Then, they cause rebar corrosion inside the concrete by destroying the protective oxide layer on the steel surface. Chloride ions reach the passive layer according to the explained pattern and they begin to react in the passive layer when the amount of chloride ions exceed the critical value and cause the perforation corrosion. Therefore, the performance of deteriorating structures can be different from the desirable performance of pristine structures. Corrosion of steel reinforcement in reinforced concrete (RC) structures is one of the main factors in increasing the vulnerability of RC structures. Due to corrosion, mechanical properties of steel involving yield and ultimate stresses, their corresponding strains, and the elasticity modulus of steel will change. Also the cross-sectional area of steel reinforcement decreases. Furthermore, after cracking, the mechanical properties of concrete will change. In this study, in order to investigate the seismic fragility and vulnerability of RC structures due to steel reinforcement corrosion, two buildings involving a 3-storey and a 7-storey RC moment frames are modeled based on the lumped plasticity model for considering nonlinearity. Two corrosion scenarios of 10 and 20 percent reduction of steel reinforcement cross section and their effects applied to the structural members of these RC frames. Then, seismic performance and the fragility of these two RC frames are investigated using nonlinear static analysis (pushover analysis) and incremental dynamic analysis. Fragility analysis results show that the probability of failure and seismic fragility of RC structures increased due to reinforcement corrosion. Therefore, fragility curves shifted to the left due to corrosion, illustrating the increase in the probability of damage at different spectral accelerations. The safety margin of the collapse of the 3 and 7-storey structures also decreased due to corrosion. For example, as a result of 20 percent corrosion scenario, safety margin of three-storey structure decreased by 16.5 percent and the safety margin of seven-story structure decreased by 28 percent. Results also illustrate that the collapse margin ratios of both structures (CMR) are reduced for 10 percent corrosion scenario. Although the probability of failure increased for 3-storey RC frame, it remains below 10 percent. However, for 7-storey RC frame, the probability of failure exceeds 10% (allowable failure probability adopted by the code) and the frame needs to be rehabilitated.

The number of waste tires around the world has been increasing rapidly in recent years and has become an urgent a serious environmental and economic problem. Today, accumulation of waste tires in the environment one of the biggest threats is to protect the environment and recycling of scrap tires is the best strategy to solve the problem. One of the methods of disposal of waste tire is to use in construction and geotechnical projects. Therefore, it is believed that the reinforced soil with tire becomes a wider application in the future, especially in countries where labor costs are low and machinery is not widespread. Eight large tire factories in the country produces an average of approximately 13.5 million tires ring. With an import of more than 4 million tire rings, an average of 17.5 million tire rings are an average annual consumption of tire. Among which on average, more than 100 thousand ring waste the production line of various factories, with tires consumed and used, and significant high volume of waste creates. In this paper, an experimental study of the soil slopes reinforced with scrap tire horizontal layer based on displacement investigated. Digital images were taken of the side of the model during incremental loading and particle image velocimetry method (PIV) was used. Some important parameters such as the length, number and location of the reinforcing tire layers are studied in this paper. Also in this paper compares the unreinforcement slope with soil slope reinforcement different arrangements and numbers of different layers with variable length (total 25 experiments) have been studied on the horizontal displacement of the slope. The results show that use of tire reinforcement has significant effects on the horizontal displacement under the footing and edge slope. The best reinforcement position is to improve the bearing capacity and lateral displacement of the upper slope. When the four-layer reinforced tire with a length of 60 cm placed in the upper half of the slope is compared to unreinforcement slope, the bearing capacity more than tripled and lateral displacement on the footing of more than 3.10 times and lateral displacement of the upper edge of the slope of more than 2.7-fold reduction. When the six, eight and nine layers of tire reinforcement with a length of 60 cm on the slope are compared to unreinforcement slope the lateral displacement under footing the substrate more than 3.5 times and the lateral displacement in the upper edge of the slope is more than 2 times lower. Three layers of tire with a length of 60 cm in the upper one-third of the slope relative to the unreinforcement slope, the bearing capacity is more than 2.3 times and the lateral displacement of the beneath footing and the edge of the slope are 1.3-1.6 times, respectively. As the length of the reinforcement layer increases, the bearing capacity and lateral displacement is reduced significantly increase. Especially when the length of the reinforcement tire is 60 centimeters, reinforcement length of the rupture wedge passes improve the bearing capacity and lateral displacement footing is significant.

Despite outstanding advances in automotive manufacturing and road construction industries, speeding still continues to contribute in increased frequency and severity of road crashes. Efforts to improve traffic safety have been primarily focused on safer roads and safer vehicles. In spite of these efforts, penalty charges and other sanctions have been shown to be an effective deterrent in changing road users' behaviour. Strengthening deterrence of speeding requires imposing effective penalties for non-compliance with speed limits, as well as effective enforcement of the legislation. Yet, different monetary and non-monetary penalties have been proposed for offensive drivers. The literature, however, lacks evidence on relative deterrence of existing penalties and the way the drivers respond to new forms of penalty systems. This study is among the first that investigated relative deterrence of different speeding penalties including “monetary fines”, “demerit point”, “car detention”, and “social deprivation”. A questionnaire was designed based on choice experiment method (CEM) with considerations of balance and orthogonality. Convenience sampling method was used to collect data in campuses of Kharazmi University in Karaj, College of Engineering in University of Tehran, and East Tehran Branch of Islamic Azad University. These campuses are among the largest university campuses in the country. Sample was recruited from those who had a driving license and were active drivers. A total of 550 questionnaires including 2004 choices were conducted (response rate: 91.1%). Most of respondents were male (70 percent) and aged less than 26 years old (82.6 percent). In 60 percent of cases the driving license was obtained in less than five years. 62 percent of respondents reported that they drove their cars less than 20 hours a week. 67 percent of male respondents and 29 percent of female respondents reported that they pay the traffic ticket on their own. Using an indirect approach, we conducted a mixed logit (ML) model to estimate the drivers’ willingness to pay (WTP) for non-monetary speeding penalties. Results showed that the investigated speeding penalties corresponded to disutility of committing the speeding violation, indicating that an increase in each of these penalties increases the expected cost of violating the speeding laws. Different penalties would induce different levels of different levels of disutility to commit speeding violations. Results revealed that “social deprivation” would offer stronger level of deterrence, followed by car detention, demerit point, and monetary fine, respectively. This finding is consistent with previous research showing that deterrence effect of increased monetary fines would be only of a limited magnitude, in the absence of non-monetary punishments. Results showed that compared to female drivers, monetary fines are more deterring for male drivers. Car detention was shown to be more deterring for those using their cars 20 or more hours a week. Increase in age was shown to be associated with reduced deterrence related to both monetary fines and demerit point. However, deterrence due to social deprivation increase with increase in drivers’ age. Findings recommend that future policies and procedures be not limited to increasing monetary fines, and take advantage of other non-monetary punishing mechanisms such as demerit point, car detention, and social deprivation.

The main material that causes aggregates to adhere to each other and forms a hard object called concrete is the cement paste. Cement paste consists of cement and water. Obviously, the higher the strength of the cement paste, the ultimate strength of the concrete made from the dough will be high. In this research, an additive material as powdered pumice of Bneh-Kohul mine near Bostan Abad and another additive as Mamaghan diatomite were added to the cement paste. Because these two materials have pozzolanic properties, they will exhibit their cementitious properties in close proximity to our cementitious materials and, as a result, are considered as cement materials. Symptoms related to the naming of different mixture ratios are clearly identified in both tables 4 and 5. In brief, the signs that contain the letter P include Pumice Powder and PD symptoms, including Pumice Powder and Diatomite Powder. The ratio of water to cement materials is considered to be 0.35 and 0.4. The results of the experiments have shown that, in terms of water absorption during treatment, all samples gradually absorb water and also show that hydration reactions of cement materials and the formation of crystals continue to occur regularly. In terms of water absorption of 28-day samples according to the ASTM standard, the results show that the porosity of our dough with different ratios of Pumice Powder  or combination of Pumice Powder and diatomite powder, and this porosity is increased by 0.35% To 0.4%. Water absorption during treatment indicates the progression of hydration reactions. While water absorption of concrete specimens at 28 days of age, according to ASTM C642-06, indicates the internal porosity of concrete, including occlusive bubbles and Capillary tubes. It should be noted that the water density of the gel was higher than that of the ordinary water and was about 1.1, and the density of the molecular water inside the crystals resulting from the hydration reactions was higher than that of the gel water. In terms of the compressive strength of doughs that only have pumice  powder additive, their 28-day compressive strength has a loss of resistance, and also for these samples at 90-day age, a slight drop of resistance is observed for the water-to-cement ratio of 0.35 However, for the 0.4% cement ratio, about 10% increased resistance. In the samples that were added to the pumice powder and diatomite powder as additive, the compressive strength changes were as follows: a) for the water-to-cement ratio of 0.35 at the age of 28 days and 90 days, an average increase of 6% Resistance is present and increases resistance for the optimum additive (25%). b) For water-cement ratio 0.4% at 28 days for 20% additive of compound powder, compressive strength reduction is noticeable, but in the 90-day life it is 5% stronger and for 25% additive compound powder at the age of 28-day and 90-day, both increase in compressive strength of 9% and 16%, respectively. Therefore, adding of the combined of Bostan Abad Pumice Powder and Diatomite Powder is recommended.

In recent years, the number of waste tires around the world is increasing rapidly and has become an environmental and economic problem. Today, accumulation of waste tires in the environment is one of the biggest problems to the environment and recycling waste tires is the best strategy to solve this problem. The use of waste tires in construction and geotechnical projects is one of the effective strategies in this regard. In this paper, experimental tests of earth slope reinforced with waste tires based on horizontal displacement (25 experiments) has been performed. During incremental loading, digital images were taken from the models and the particle image velocity (PIV) method was used. Parameters such as tire layer length, number of layers and tire layer position are considered as variable. The results show that the use of tire reinforcement has a significant effect on reducing horizontal displacement under the foundation and slope surface. Horizontal tire rows are the best reinforcement location in terms of improved bearing capacity and lateral displacement. When four layers of 60 cm long reinforcement tire are placed in the upper half of the slope, the bearing capacity increases 3 times and the lateral displacement under the foundation decreases by 3.1 times. When three layers of tires with a length of 60 cm are placed in the upper third of the slope, the bearing capacity increases by 2.3 times and the lateral displacement under the foundation increases by 1.3 times. When six, eight, and nine layers of reinforcing tires with a length of 60 cm are placed into the slope, lateral displacement under the foundation is reduced more than 3.5 times. In Iran, eight largest tire factories produce 13.5 million tires in a year. It also imports 4 million tires a year. Therefore, 17.5 million tires are the annual consumption of the country. More than 100,000 tires are the product of factory production line waste, as well as used tires. Waste tires have been used to strength retaining walls, foundations, improve soil properties, embankments and etc. Therefore it is believed that soil reinforced with waste tires become a wider application in the future, especially in countries with low worker costs. In this paper, the test was performed in a box with length, width and height of 2, 1, 1 m, respectively. The test material used in this study is sand in the dry state. The maximum and minimum dry sand densities are 19.43 and 16.36 kN/m, respectively. Internal friction angle and cohesion were measured by direct shear test at 38 degree and about 0 kPa, respectively. Digital images taken from the front of the test box during the experiment. Images were processed using GeoPIV software developed at the University of Cambridge. The results of this study are as follows:1. The best position in terms of bearing capacity and lateral displacement is to use four layers of reinforcing tire in the upper half of the slope.2. As the length of the reinforcement layer increases, the bearing capacity increases significantly and the lateral displacement decreases. Especially when the length of the reinforcement tire is 60 cm and the length of the reinforcement passes through the rupture wedge, the improvement in bearing capacity and lateral displacement of the foundation is noticeable.3. The best position in the three layers of reinforcement tire on the slope in terms of bearing capacity and lateral displacement is one-third of the upper slope.4. The presence of a tire in the lower third of the slope has little effect on improving the bearing capacity, lateral displacement of the foundation and the slope surface compared to the slope without reinforcement.

Clay soils often cause problems in construction projects. In cold regions, freezing and thawing of clay soils can cause significant changes in the geotechnical characteristics of the soil. Frozen and thawed soils have shown changes in volume, strength, compressibility, frozen moisture content, bearing capacity and microstructural changes. In road construction projects in cold regions, freezing and melting is one of the factors affecting the unstability of soil engineering behavior, including the durability and performance of pavement and pavement layers.  Therefore, the purpose of this research is to evaluate the effect of freezing and melting cycles on the parameters of the durability of calcareous stabilized clay bed based on compressive strength test results. 400 kg of soil samples were collected from the subgrade of the RAZ-PASIN rural road. In the first stage, granulation experiments, Atterberg and ... on 20 soil samples were performed. The second stage was the dry maximum dry matter and optimum moisture content of the soil-cement mixture. The third step was to determine the percentage of suitable cement for mixing, soil-cement mixed density with different percentages (6%, 8%, 10%, 12% and 14%) with limestone cement type 1 and type 2. In the fourth stage, 24 cylindrical specimens were added to the soil sample by adding (8%, 10%, 12%) of type 1 and type 2 calcareous cement and tested for compressive strength. In the fifth step, the indirect tensile strength and the stress-strain modulus of the mixed soil-cement were determined. The results indicated that the maximum dry matter density of the soil-cement mixture was obtained by adding 10% of type 1 and type 2 calcareous cement. The results also showed an increase in the compressive strength of the composite made with type 1 lime Portland cement compared to Type 2 lime Portland cement, and all specimens containing 8% calcareous cement additive exhibit more than 35 kg / cm2 after 7 days of resistance treatment. This means that samples made with Portland cement have a sufficient durability against atmospheric agents. If the use of calcareous Portland cement is used only for bed consolidation as a layer of pavement layers and the appropriate weight percentage of Portland Type II cement is selected to be 8% for the consolidation of the studied soil, the cost of the Rural Road Project will be compared. The Late Valley showed a 13% reduction in the cost of supplying calcareous Portland cement compared to Type II Portland cement (Table 10). This is due to a 15% reduction in energy costs (gas and electricity consumed) in the manufacture of calcareous Portland cement compared to Type II Portland cement. By comparing the results of compressive strength of soil-mixture of type 1 calcareous Portland cement and type 2 cement, it can be concluded that the effect of type 1 calcareous Portland cement in obtaining compressive strength is better than type 2 calcareous Portland cement due to increasing Lime is made of cement composition. This increased resistance is due to the ion exchange reaction and the agglomeration-compaction reaction between lime and soil and is achieved by lime contact with most fine-grained soils. Thus, the calcium ions in the lime are replaced by the lower-capacity positive ions in the soil. This results in the accumulation of calcium ions around the clay particles.

Today in the world, including in our country, the use of nuclear technology in various fields of power plants, industry, agriculture and medicine is expanding. One of the most important issues in nuclear technology is nuclear radiation protection to prevent harmful environmental, pathogenic and harmful effects on some of the precision measuring instruments. From the perspective of preservation, all the radiation and particles are not of the same importance, because their penetration and impact on different materials, such as living tissue, are not equal. In the discussion of conservation, neutron and gamma radiation is of particular importance because, due to its unloaded nature, they can pass relatively large thicknesses of the shield and contribute to raising the dose rate outside the shield. In addition to the many uses of radioactive waste, it should be noted that this radiation damages cells and living tissues and protection against it is essential and inevitable. In order to protect against radiation, absorbent materials should have a high density, high attenuation coefficient, and structural properties with high strength, easy to provide and cheap production. According to the above, the use of concrete is a suitable alternative for radiation protection. Due to its high specificity and low cost, barite is widely used in the oil and gas drilling industry, coloring industry, pharmaceutical plastics (due to the absorption of radioactive wastes), chemicals and so on. So it can be a good option for gamma radiation protection. In this research gamma-ray linear attenuation coefficient and neutron beam dispersion cross-section of two series of concrete samples containing barite powder as a substitute of sand with and without graphite powder under gamma rays with Cs-137 fountain and NaI (Tl) detector under neutron beam With the Am-Be 241 fountain and the BF3 detector. The compressive strength, tensile strength and ultrasonic pulse velocity were also determined. All concrete samples, with the exception of control samples, have been made with 400 kg / m3 cement and 0.4 water/cement ratio with 10% microsilicon replacement in two series. In the first series, barite powder was replaced with 10, 25, 50, 75 and 100% replacement of sand, and in the second, 10% of the graphite powder was added to samples containing various powdered barite powder. The result of this study showed that a sample containing 10% barite powder plus 10% graphite powder could be an optimal amount for a concrete protected against gamma and neutron rays.

Concrete due to its special feature, is the most widely consumed material in the world, after water. But the production process of ordinary Portland cement as a main component of conventional concrete, has major disadvantages such as high amount of CO2 emission and high energy consumption. Therefore, it seems necessary to find an alternative to ordinary Portland cement. In recent years, geopolymer has been introduced as a novel green cementing agent and environment-friendly alternative to the Portland cement which can eliminate the extensive negative of ordinary Portland cement production process. According to the needed engineering characteristics perspective in civil engineering, the geopolymer concretes have better chemical and mechanical properties than the ordinary ones such as high compressive, flexural and tensile strength, rapid hardening, resistance against high heat and firing, low penetration, resistance against salts and acids attacks, and low creep. On the other hand, in terms of technical characteristics, concrete has some disadvantages, most notably low tensile strength and consequently low ductility. Therefore, the use of different fibers in the concrete mixture and the manufacture of fiber reinforced concrete is considered as an appropriate solution to eliminate these defects. Also, fiber reinforced geopolymer concrete is known as a novel type of concretes with higher ductility than ordinary concretes. In this experimental study, two types of polymer fibers, including simple polypropylene fibers and 4-element polyolefin hybrid fibers, were used to manufacture fiber reinforced geopolymer concrete specimens. In this regard, fiber reinforced and non-fiber geopolymer concrete specimens were made and cured in 80 °C for 24 hours. After curing, specimens were placed in the ambient condition and associated tests including: density, 3-days water absorption, 7-and 28-days compressive, Brazilian indirect tensile and three point flexural strengths, were performed to study effect of fibers on metakaolin-based geopolymer concrete mechanical properties. Also, to study effect of fibers on high-temperature resistance of metakaolin-based geopolymer concrete, specimens weight and compressive strength loss percentage after exposure to high temperatures up to 800 °C, were measured. The obtained results indicated that using fibers in geopolymer concrete mixture, result in increasing compressive, indirect tensile and flexural strengths and also decreasing in density and 3-days water absorption. Further, the use of hybrid fibers due to their ability to inhibit the cracking process from both micro and macro levels, significantly improved compressive, indirect tensile and flexural strengths compared to simple fibers. The optimum amount of 4-element polyolefin fibers for compressive, tensile and flexural strength improvement was measured 0.2%, 0.2% and 0.15% (by volume), respectively. Also, the optimum amount of polypropylene fibers for compressive, tensile and flexural strengths improvement was measured 0.2% (by volume). In term of high-temperature resistance, although the polymer fibers reduced the risk of the explosive sapling of geopolymer concrete specimens due to generation micro channels which were randomly distributed in concrete because of melting of fibers, resulting in less weight loss than non-fiber specimen, but on the other hand, the compressive strength loss of polymer fiber reinforced specimens were higher than non-fiber one. Overall, it can be concluded that these fibers did not have a significant effect on the high-temperature resistance of geopolymer concrete.

Sand and gravel are essential materials for developing purposes in infrastructures and many various purposes. Iran, is a developing country and numerous infrastructure projects all around the country are under construction. This issue, demonstrates the growing demand for sand and gravel harvesting. Irregular and non-technical harvesting of sand and gravel from rivers, plays an important role in unwanted morphological and environmental side-effects. Physical modeling and numerical simulation are two main techniques to investigate this phenomenon. Considering the high cost of constructing physical models, application of numerical tools for simulation of hydrodynamics and sedimentation has made a significant help for understanding the related phenomenon including the effects of sand and gravel removal in different rivers. In this study, the accuracy of the MIKE21 as a two-dimensional numerical tool, in simulation of sand harvesting hole displacement was investigated by comparison with laboratory data. For this purpose, nine experiments with different dimensions of excavation holes were designed in a 10 m long and 0.7 m wide laboratory flume with uniform sand bed materials. (D50=0.71mm). Two types of triangular and trapezoidal excavation holes were tested. Four important point plus depth and area of the excavated hole were considered as base points of comparison between simulated and experimental results. The flow depth was constant during all experiments (12 cm) and clear water condition was considered (v/vc=0.95). Acceptable agreement between numerical and experimental results was observed. However, the accuracy of the model was more in larger holes whereas the maximum error in predicting the migrated hole geometry in trapezoidal holes was about a half of triangular ones. After verifying the numerical model in laboratory, a specific reach in Helleh river was considered as a case study. Initially one-dimensional model of the river was simulated with HEC-RAS. 25 years return period flow hydrograph was introduced as the upstream boundary condition. Normal flow depth at Helleh Lagoon and time series of the water surface elevation changes of the Persian Gulf were introduced as two downstream boundary conditions. The boundary conditions of the selected reach for   two-dimensional modeling were extracted from one-dimensional simulation. After setting up the two-dimensional model, the effect of sand and gravel mining on a bridge in the reach was investigated in two different scenarios. The distance of the sand mining hole to the bridge was selected as 1000 m and 100 m respectively in two scenarios. It should be noted the simulation was conducted only for a 25 years return period within 16 days. More severe floods can leave more significant effects on the river and in-line structures. The results indicated that for a flood event with a return period of 25 years which was considered for simulation, sand and gravel mining had changed the hydraulic parameters and bed profile significantly, so that the flow depth at the vicinity of the excavation hole was raised up to 77% in second scenario. The flow velocity was reduced up to 75% in the first scenario and the bed profile was decreased up to 1.27m at the foundation of the bridge in the second scenario. Initial signs of river meandering were emerged in the second scenario where the flow was deviated to the mining hole.

Predicting the residual load-bearing capacity of damaged concrete-filled steel tube (CFST) columns exposed to fire, based on the effects of eccentricities, is a subject on which relatively little research has been done. This paper aims to present the results of a series of post-fire residual capacity tests for CFST columns with different cross sections (circular and square), under axial load, and different eccentricities in the event of a failure. In this experimental study, the influence of parameters such as cross-sectional shape, load eccentricity, slenderness and fire protective coating on the post-fire residual capacity of CFST sections was investigated. Based on the results of this study, the following conclusions were obtained in the scope of this research work:The results showed that eccentricity could be effective in reducing the residual capacity of the column, but the change in the amount of eccentricity cannot be as effective as reducing the residual capacity of the columns. The studies indicate that the residual capacity is significantly reduced by increasing the slenderness ratio. Therefore, in order to determine the residual capacity of the CFST columns under load eccentricity, a simplified equation for predicting the reduction factor was proposed, a comparison between the predicted and experimental results shows that there is a reasonably good agreement. The tests show that by increasing the temperature over a cross-section of CFST columns, the residual axial load capacity and the axial stiffness of the unprotected columns decreased significantly compared to the unheated columns. Comparison of the axial compressive capacity of CFST columns with square and circular have shown that for columns having the same concrete material, the circular column has slightly better structural post-fire behavior than the square column. To fire-protected sections, the effect of the cross-sectional shape on the residual strength is significant, relative to the unprotected sections is more. In fact, by comparing the temperature distribution on the surface of the circular and square sections, one can find that the maximum temperature distribution at the circular cross sections is less than the square cross sections. Therefore, with less degradation of the properties of the cross-sectional materials, the more residual load-bearing capacity is expected. Finally, based on the experimental results, the ability to predict the residual load-bearing capacity of the concrete-filled hollow tube columns after exposure to the ISO-834 standard fire as per the modified design method in Eurocode 4 for the fire and ambient conditions were evaluated. The investigation’s results showed that the simplified method of Eurocode 4, in the ambient temperature produced safe results for predicting residual resistance of CFST columns after fire exposure, under both concentric and eccentric loading conditions. This approach was considered as a conservative method, with the MPEs for concentric loads, as well as both concentric and eccentric loads as -5.51% and -3.06% lower than the prediction, respectively.