نشریه مهندسی عمران
سال پنجاه و دوم شماره 10 (دی 1399)

One of the most important ways to cope with this problem the instability of the well wallis to determine the optimal drilling mud pressure. The pressure of the mud should be so high that it is in proportion to the amount of tension in the pores and pockets, and to the extent that the well after the large tensile fractures caused by the high pressure of the mud, as well as the shear fractures due to low pressure It will be safe. The aim of this study was to obtain a relationship to estimate the optimal drilling mud pressure in wells in the oil-rich regions of southern Iran. To achieve this goal, information of a number of oil wells was collected in the oil fields of southern Iran and then, using FLAC2D software, a limited-scale numerical program limited to oil wells, oil wells were analyzed in two Equilibriums and equilibriums modes have been investigated. Ultimately, for determination of the stability of the optimum drilling mud in the elastoplastic method, the method of determining the normalized level of NYZA has been used. In each step, optimal drilling mud pressure is calculated and finally, a correlation is presented using SPSS software through multivariate linear regression. This relationship is a linear relationship in which the optimal drilling mud pressure is estimated by parameters of minimum and maximum horizontal tensions, pore pressure, internal friction angle and adhesion.

Today, many elements are used to control vibrations and reduce structural damage. Pall friction damper is one of these elements. This energy-dissipating damper can help to reduce structural damage. Various loads such as seismic and blast impose significant amounts of energy on the structure. This energy must be absorbed or dissipated by structural elements to create a new energy balance in structures. In this research, tried to investigate the performance of a ten-story building with a pall fraction damper under blast loads using the concept of energy balance in a structure. Tow ten-story steel MRF structure whit Pall fraction damper are exposed to 12 blast loadings and their performance has been investigated using the concepts of plastic hinges, drift and strain energy of plastic. The results of the study show that the plastic hinges, the story drift and the strain energy in structural elements in the model with a frictional pallet damper are less than the model without a damper. The dissipated energy in the pall friction damper reduces the contribution of plastic strain energy to other members, and reduces structural damage.

AlNajaf city considered one of the gypsiferous rich soils cities in Iraq. When a building is constructed on gypsiferous soil in unsaturated state, it doesn’t have a settlement, but when a gradual saturation is occurred, the soil gives a shape deformed and may be collapsed. This paper presents how the degree of saturation can affect on shape deformation of a gypsum sand soil. A triaxial test device has been modified to have the ability for unsaturated tests. The soil samples were taken from Al-Najaf city in Iraq. A disturbed samples with two different gypsum contents; 14% and 29%, are tested with presence of different matric suctions, initial matric suction, 60% initial matric suction, 30% initial matric suction and zero matric suction. A loading-path was adopted to symbolize when a construction is built on a gypsiferous sand soil in a specific matric suction (specific degree of saturation). In addition to the previous tests, two conventional saturated tests (CD) were added under the above mentioned of confining stresses. The results were when increasing matric suction, the stiffness and shear strength are reduced and the volumetric strains increase significantly. The percentage increases are 60% and 50% under confining pressure of 100 kPa and 200 kPa, respectively for the two selected gypsum contents. The results of this study can be used to estimate the settlement that results from decreasing matric suction due to water table rise or other phenomena.

Retaining walls are walls that maintain the pressure caused by the existing state of the difference in levels caused by embankment, excavation or natural factors. In this study the stability of the flexible walls and the type of reinforced soil walls are evaluated to examine the stability and design the retaining walls with reliability method which gives more realistic results than other design methods. Reinforced soil wall is a special material that is formed by the combination of the soil and the reinforcement member. Basically the soil is weak in stretching and cutting and the idea of reinforced soil wall is in fact the solution to this problem. There are many uncertainties in civil engineering and in particular in the geotechnical discussions the discussion of the uncertainty of the parameters is much more evident because the anonymity of the soil behavior. The traditional methods of evaluated the stability of reinforced soil walls which are usually based on empirical judgments such as the concept of a coefficient. Efforts to quantify uncertainties causing genesis of probabilistic methods. Probabilistic analysis in comparison with definite analysis the uncertainties in the calculations and instead of using the confidence coefficient in the project safety level it usually uses the probability of failure or the reliability index

One of the mechanical methods of soil stabilization is the use of reinforcing elements such as geotextiles, geogrids and natural or artificial fibers. In recent years, the use of disconnected artificial or natural fibers has become commonplace with random distribution to improve the mechanical properties of soil. A new type of fiber that has a natural origin and its production and application has the least environmental impact is basalt fiber. The prominent advantages of this type of fiber are the high resistance in acidic, alkaline and saline environments, and mechanical properties that are competitive with other fibers. In this study, in addition to identification tests, a series of modified compression test, uniaxial compressive strength test and indirect tensile strength test and SEM electron microscopy was tested on clay stabilized with basalt fiber with random distribution. The focus of this research was mainly on the effect of fiber length and weight percentage on soil resistance parameters. For this purpose, basalt fibers were mixed with soil in weight percentages of 0.25, 0.5, 0.75, 1, 1.5, 2 and with three different lengths of 6, 12, 25 mm, then compressed with optimum moisture content. The results show that by increasing the weight percent and length of the fibers, compressive strength and tensile strength, initially increases and then decreases. But in general, the compressive strength and tensile strength of the reinforced soil is more than unreinforced and in all cases, reinforced samples are more ductile than unreinforced specimens.KEYWORDS

In many overflow structures such as vertical drops, using the flow energy dissipator and investigating the subsequent effect on the hydraulic parameters are the most important issues in hydraulics. This study experimentally investigates the behavior of hydraulic parameters through the utilization of combined screens (horizontal-vertical) in vertical drops. The results revealed that the utilization of the screens combined with vertical drops reduces the relative mixing length and increases the relative pool depth and relative energy loss with respect to a simple vertical drop. It was also observed that the increase in the relative critical depth result in the increase in the relative wetted length of the vertical screens, the relative mixing length and the relative pool depth, and decrease in the relative energy loss. Evaluating the total energy dissipation of system by the effective components of energy dissipation exhibited that, by increasing relative critical depth, the performance of vertical drop equipped with horizontal screen decreases and the performance of vertical screen increases. However, the contribution of vertical drop equipped with a horizontal screen is more than 82% of the total energy loss of the system. Also, increasing the porosity of screen reduces the relative wetted length of horizontal and vertical screens, the relative mixing length and relative pool depth, and increase the relative energy loss.

Precipitation is one of the most important components of water cycle and plays an important role in assessing the climatic characteristics of each region. Estimates of monthly rainfall are important for various purposes such as flood estimation, drought, irrigation planning, and river basin management. In the present study, the monthly rainfall of Tabriz station was investigated using the intelligent Gaussian Process Regression (GPR) method based on Complementary Ensemble Empirical Mode Decomposition (CEEMD) and Wavelet Transform (WT). In this regard, different models were defined based on teleconnection patterns and climatic elements, and the impact of different input parameters was assessed. The obtained results from the models proved the high capability and efficiency of the applied method in predicting the monthly precipitation. It was observed that in prediction of the monthly precipitation, NAO, Nino3, MEI and climatic elements including mean monthly temperature and relative humidity, as well as precipitation related to the previous months, are effective in prediction and improve the models accuracy. The results showed that time series decomposition based on wavelet transformation led to more accurate outcomes compared to the complementary ensemble empirical mode decomposition. The best evaluation of test series using wavelet transform decomposition was obtained for the state of modeling based on teleconnection patterns and climatic elements with the values of DC=0.889, R=0.961 and RMSE=0.036. Also, based on the sensitivity analysis, Pt-3 was found to be the most effective parameter in modeling.

One of major parameters in determining shear capacity of beams is the height of beam. Researches show that with increase in beam’s height, normalized shear strength decreases which this phenomena is called size effect. In recent years due to advances in construction methods, the idea of using lightweight concrete deep beams has been proposed, this should be done with a full understanding of the behavior of lightweight concrete. Moreover, truss models are recently used for analysis and design of deep beams in codes which their validity for lightweight concrete should be investigated.In this research to investigating size effect in lightweight concrete deep beams and comparison with normal concrete, two series of beams including 8 deep beam with shear span to height ratio of 0.5 were built in lab. First series included 4 beams with height of 30, 45, 60 and 90 cm using lightweight concrete in their construction, specimens of second series were similar to first but normal concrete was used in there construction. Results show that normalized shear strength in both groups of beams decreases with increase in height but the intensity of this decrease in lightweight concrete deep beams is more than normal concrete which shows that size effect in lightweight concrete is more than normal concrete. Results of Experiment were compared to truss methods in codes and some of proposed models in codes. Results indicate that all methods are conservative in low height beams and with increase in height, safety margin decreases.

In general, underground structures exhibit nonlinear behavior when applying dynamic loads such as earthquakes and explosions. One of the most important parameters for loading, analyzing and designing this type of structures is the dynamic load factor of the behavior coefficient. This coefficient contributes to the nonlinear behavior of the structure in linear analysis, or in other words, is a factor affecting the nonlinear behavior of the structure in linear analysis. By applying this coefficient, linear analyzes can replace conventional nonlinear analyzes in the analysis and design of explosive-proof structures, which are mostly time-consuming and complex. Investigations show that the acceptable amount or range for reduction factor of concrete coating of underground structures under the influence of explosive loads is not determined totally. To find this factor, the tunnel structure must first be modeled by a software that is able to calculate the interaction between the structure and the soil. In this research, plastic hinges were introduced into the SAP2000 software, and a pushover analysis was carried out on a concrete coating of a tunnel under an explosive charge pattern By output of this analysis, the force-vertical displacement diagrams is plotted for each of the tunnel performance levels and the Reduction Factor is obtained for pattern of explosive charge by using the relationships that explained in paper. It can be seen that the Reduction Factor for such structures depends only on the two parameters of ductility and over strength of structure.

Helical anchors with unique characteristics have several applications in constructing and reforming the foundations, as well as soil improvement. However, a limited number of study has been done on the use of helical anchors in walls and slopes stability. In the performed studies, the behavior of the helical anchor’s wall was investigated. For this purpose, a laboratory study was designed to evaluate the wall stability with three types of helical anchors and two types of back-slopes in sandy soil. The aim of the study was to investigate the effect of anchor’s shape and the back slope above the wall on the wall crest displacement. To increase the accuracy of measurements and determine the shear strains, photogrammetry and particle image velocimetry (PIV) methods were employed. Finally, to evaluate its implementation potential, the results were compared with those of the nailing method. The results of modeling revealed that an increase in diameter and the number of the helices led to decreasing in wall crest displacement. The reduction percentages were 30% and 60% respectively for increased diameter and increased number of helices and diameter. If the significant reduction in displacement is required, it is suggested to increase the number of helices without any changes in their diameter. Besides, anchors need a small amount of displacement to be activated and this issue cannot be solved by changing the type of helical anchor. Finally, the results indicated that the slip surface created on the wall of helical anchor using light surcharge is parabolic in shape.

Jet grouting method is considered as one of the most widely used improvement methods among the others and is applicable in most geotechnical problems such as increasing load capacity, reducing settlement, creating seals, stabilizing slopes, etc. One of the challenges faced by designers is finding the strength and geometry of the elements made using this method. The most effective components in the resistance of jet grouting columns are the type and parameters of injection, soil characteristics (such as aggregation), the amount of cement inside the sample, water to cement ratio of slurry, the type of cement and the method of sampling (coring or wet sampling). In this paper, after the construction of jet grouting columns in the laboratory and taking core of them, the impact of coring on uniaxial compressive strength is studied. Also, the point load test was used to study more about the strength parameters of the microjet grouting columns. Based on the results, the compressive strength of microjet grouting columns is high (up to 59 MPa), and these values are confirmed by the point load test. It was also observed that with increasing speed of soil-cement columns formation, compressive strength decreases. Based on the compressive strength results, coring reduces resistance by 60%. Also, the cores taken in the horizontal direction showed about 33% less uniaxial compressive strength than the vertical cores.

In this study, to investigate and compare the performance of the single mass damper in the maximum modal displacement (roof) and multiple mass dampers vertically distributed in the height of the structure, based on the modal analysis, two linear and nonlinear models of a 40-story structure were selected. The structure has been modeled in OpenSees software using seven acceleration time histories. The analysis results for applied earthquakes under the maximum acceleration of 1.0g show that the control of the linear structure by multiple tuned mass dampers (MTMDs) tuned to the first and second modes have more appropriate behavior than others, and the average reduction of the maximum displacement of the Roof applying this type of dampers is 14.5%, which is about 2 times more than reduction of the STMD tuned to the first mode and the MTMDs tuned to the first or second modes, systems. However, due to the assumption of tuning the design parameters of the dampers corresponding to their elastic behavior, the performance of single and multiple mass dampers slightly decreases in a nonlinear model of the structure while structural responses are still controlled. Also, for the 10% error caused by misadjusting of the dampers, the behavior of MTMDs is more appropriate.

The present study was conducted to compare the efficiency of normal and modified UASB reactor for the treatment of dairy wastewater. To conduct research, two reactor units with a height of 120 cm and a volume of 48 liters have been used on a laboratory scale and a tank septic tank and an additional sludge blanket have been used to optimize the UASB reactor. Initial inoculation of the reactor was carried out using sewage treatment sludge (active sludge method) slaughterhouse, along with fresh cow discharges and feeding using dry milk. The research lasted for fourteen periods for 154 days, the first period for 30 days including the design and construction of the reactor, the second period for 40 days including starting, forming granules and measuring PH, the third period for 40 days including the continuation of the process The formation of granules and sludge blankets, pH measurements, and preliminary analysis of the removal efficiency of COD and the fourth period for 44 days include the continuation of granulation sludge measurement, PH and the evaluation of COD removal efficiency. The organic loading during four periods was 5.2-11.4 kgCOD/m3.day, and the reactor temperature was in the second to third period in the mesophilic temperature range and during the fourth period at the mesophilic and psychrophilic temperature range. The retention time in the studied period is 24 hours. The output COD yields four to for normal reactor 75-60% and a modified reactor of 94-60%.

In recent years, the use of Roller–Compacted Concrete Pavement (RCCP) has developed in road pavement due to its great advantages. Adding fibers to RCC can improve some properties of the concrete, including flexural strength, fatigue resistance, crack growth rate, and shear transfer along cracks and joints. Many experiments have shown the advantages of using fiber-reinforced concrete in RCC, but more information is needed about their behavior in cold regions, and especially the exposure to Freeze-Thaw cycling. Investigation and comparing the effect of polymer fibers on the strength and durability of Roller-Compacted Concrete under Freeze-Thaw cycling are the main goal of the present article. Therefore, specimens with weight percentage of fiber equal to 1, 2.5, and 4% (by weight of cement) and fibers of to 5, 20 and 40 mm lengths are made. Durability test against a Freeze-Thaw cycling and compressive strength are measured on samples after 7, 28 and 90 days. Analysis of the results shows that the additive fiber increases the compressive strength of the RCC, but decreases its durability against the melting and freezing cycles. Therefore, the use of fibers on RCC in cold regions should be done due accuracy and attention.

Gravity currents, also known as density currents, or turbidity currents, are happened by the density difference between the flow and its ambient fluid. The density difference can be due to suspended particles, chemicals, soluble materials, and temperature differences. In dams reservoir ambient fluid, usually has a vertical stratification. When the gravity current arrived to ambient fluid, in the position that density of both gravity current and ambient fluid is equal the gravity current abandon the bed and flows in ambient fluid horizontally. Therefore the density current into this reservoir maybe intrude such as interflow density current.This study investigates the inter flow density current in a stratification ambient. The investigation of velocity profiles showed that the flow is self-similar and velocity fluctuations Continues maximum up to 2.5 times greater than current thickness in the lower layer. The front velocity of currents in stratified environments increases at first then sizeable decreases. It shows that stratified can limited the flow movement. In each three slope, increasing of discharge and concentration increase velocity head of density current in stratified environment. As the slope increases, the current velocity increases at the underflow stage, and in the interflow stage, the slope does not have much effect on the current velocity. Interflow Travel Time decrease in increasing of discharge and concentration. Density current in weaker stratified can travel more distance in the slope and separate latter from the bed.

Achieving the lowest emission rate of urban air pollutants, requires an effective management of mobile air polluting sources. To address this type of management, not only high quality vehicles should be recruited but also the quality of transportation such as amount, slope, and traffic patterns (i.e., steady vs. interrupted flow) should be considered. Therefore, a number of methods are emerged to control the steadiness of traffic flow through traffic network instruments such as traffic lights or ramp metering schemes. In this study, attempts have been made to model a steady traffic flow on the Sadr Overpass to mitigate the least air pollutants production Modeling the optimized traffic volume entering and leaving the ramps whilst maintaining an acceptable service level using a mathematical linear programming technique is presented. Furthermore, a simulation has been conducted using an IVE model to estimate the amount of emissions. The results indicate that temporary closure of ramps in the east-west direction could lead to a steady flowrate on the overpass which decreases the amount of CO and NOx by %54 and %25, respectively. Similarly, in the West-East direction, deploying a cyclic monitoring of traffic flow in the ramp discharging into Modarres Expressway, results in reduction of CO and NOX by %42 and %41, respectively.

The leak detection parameters in the inverse transient analysis (ITA) are obtained in an inverse approach by solving a nonlinear programming problem using metaheuristic algorithms such as the genetic algorithm (GA). Despite its high capability in deriving the leak detection parameters, the ITA method is computationally complex and costly as it uses the (GA). The reason can be attributed to the random behavior and gradual evolution of this algorithm inspired by the nature. This study aimed to increase the computational efficiency by employing surrogate models in the optimization process of the ITA method. The surrogate model is in fact a simulated sample of the main model capable of approximately calculating the objective function in a fraction of a second. The way these models are integrated into the optimization model highly affects their success or failure. To this end, two algorithms incorporating population-based surrogate models, namely (Pre-selection Strategy) PS and (Best Strategy) BS, were presented. To evaluate and compare the results, a distribution network was used to identify the leak detection parameters. The results indicated an increase in the computational efficiency compared to the ITA method integrated with the (GA). The PS algorithm demonstrated the highest performance by reducing the objective function and time complexity by 58% and 78%, respectively.