جستجوی مقالات مرتبط با کلیدواژه « Roughness » در نشریات گروه « عمران »

Estimating the safety and comfort of the occupants of a road-using vehicle is one of the most important issues facing researchers in the field of road and road safety. Road safety is examined in different branches. One of the most important parts of road safety assessment and maintenance management is the assessment and monitoring of road surface failures. The Road Roughness Index (IRI) is used for this purpose. . In order to evaluate the path of the road, in addition to evaluating the geometric design, it is also necessary to evaluate the geometry of the faults. If a criterion can be found to assess the situation, the critical state of the criterion can be found and if it reaches a critical state, the road condition can be considered unsafe or in need of improvement. In this research, the dynamic response of the vehicle while moving on roads with different rough shapes but with the same IRI (the case where the two-wheel IRI of the vehicle is equal to 10) is simulated by the software. In addition to examining the dynamic response of the front axle of the vehicle (due to the application of more force on the front axle) on common parameters such as: vertical acceleration, maximum vertical acceleration and the minimum root of vertical acceleration, to determine whether in a symmetrical roughness, again a response Is there dynamics for the left and right wheels? If a clear relationship can be established between the roughness created by the definition of the IRI index at the road surface and the shape of the roughness (wavelength and amplitude), it is possible to prioritize the breakdowns with critical wavelengths (most inconvenient). The results show that by further examination of the vertical acceleration at different speeds, it can be seen that in the amplitude of longer waves, the highest values ​​of vertical acceleration entered by the vehicle at speed. High speeds occur and also maximum vertical acceleration values ​​occur at lower wavelengths at lower speeds. For example, in parabolic failure, the maximum acceleration values ​​for the wave amplitudes of 0.1(m), 0.05(m), 0.01(m), 0.005(m) occur at speeds above 60 km / h. Vertical acceleration values ​​for wave amplitudes of 0.0025, 0.0015 and 0.001 occur at speeds of less than 40 km / h. At a speed of nearly 80 km / h, the value of the vertical acceleration of sinusoidal roughness (according to IRI) shows a significant difference of about 0.2 m / s relative to the parabolic.

This research aims to present a novel approach for retrieving soil parameters from the combination of Sentinel-1 satellite data and the OH model. This information can aid in improving land management and increasing agricultural productivity. Accurate determination of soil parameters such as roughness and moisture is crucial for efficient land agriculture management and decision-making. Conventional ground-based methods for obtaining these parameters are often limited in spatial coverage and are frequently found to be time-consuming and costly. On the other hand, remote sensing techniques, especially those utilizing SAR satellite data, offer the potential for a more effective and comprehensive solution for monitoring soil conditions in vast areas. This study focuses on three main questions related to soil roughness and moisture parameters, emphasizing their significance for agriculture and their impact on soil science and agricultural processes. It also underscores the potential of remote sensing techniques, particularly the acquisition of satellite data, in providing effective and comprehensive solutions for monitoring soil conditions in extensive areas. Soil roughness and moisture are highly important for agriculture and can have significant impacts on crop growth.

This research is focused on investigating and analyzing the soil moisture and roughness parameters of an agricultural land in Nazarabad County. The process includes data collection, preprocessing, radar data calibration, and validation. Radar data for this study is obtained from the Sentinel-1 satellite. The use of radar data from this satellite for monitoring agricultural lands day and night and conducting comprehensive research on the subject is highly valuable. The input data underwent preprocessing in the SNAP software, involving the use of filters to remove noise spots and geometric corrections. The necessary inputs for solving the OH model equations from polarized images, especially HH and VV, were obtained after the aforementioned settings using SNAP software. Statistical analysis involves extracting vital information such as Sigma Naught (σ) and incidence angle (θ) for each pixel, which are crucial for the OH model. Polarized images, after adjustments, were further used for analysis. Next, the equations written for each pixel were individually solved in MATLAB programming software, and the values of the root mean square height (s) for obtaining roughness and the dielectric constant (ε) - a key parameter for estimating soil moisture content, i.e., soil moisture (mv), for all pixels were obtained. Finally, matrices related to these values were transformed into the output image, generating a map displaying information on soil moisture and roughness.

Based on the results obtained, it has been demonstrated that the values of dielectric constant, roughness, and humidity are very sensitive to the initial solver parameters. In particular, the dielectric constant exhibits significant sensitivity, which may be reduced by improving the solution method. Roughness profile analysis shows that the rms height varies in different regions and increases the scattering with the increase of roughness. Additionally, moisture content analysis indicates that the humidity is relatively uniform throughout the area.

This study demonstrates that the use of Sentinel-1 satellite data in conjunction with the OH model leads to a significant improvement in access to reliable information for enhancing agricultural management. This approach has the capability to analyze spatial and temporal variations in soil roughness and moisture, providing vital information for optimizing agricultural practices. Substantial soil condition improvements lead to more precise monitoring and better productivity in agriculture, offering the potential for more accurate monitoring of soil conditions and enhanced productivity in the agricultural domain. These assessments can provide valuable insights for agricultural land management and decision-making processes, contributing to increased efficiency and environmental conservation.

Evaluation of mechanical behavior of the soil-structure interface has been the focus of many researchers as an effective factor on the strength performance and deformation of the structure. Since the interaction of the structure and the soils around it will have a great impact on the soil bearing capacity, it is important to study the physical conditions. In this study, taking into account the curing time, effect of using Persian gum and the roughness of the steel on the behavior of the soil-structure interface using large-scale direct shear test have been investigated. The Persian gum was used in three amounts of 0.3, 0.6 and 0.9% on three smooth, rough and geotextile covered surfaces. Based on the results, by injecting Persian gum into the soil-candle interface, the adhesion between soil and contact surface increases by about 20 times and the internal friction angle increases by one degree. The rate of increase of strength parameters decreases with increasing curing time.

One of the most important problems in hydraulic structures is the kinetic energy of the flow. If this destructive energy is not controlled, the structures downstream will be damaged and cause significant damage. One of the functions of energy dissipator structures is to change the flow regime, reduce the flow velocity and eliminate excess flow energy. One of the methods that can deplete the flow is to create a narrowing along with the roughness in the flow path. By creating a constriction in the flow path and using roughness in the constriction wall and forming a hydraulic jump, a significant part of the destructive energy of the flow can be dissipated. Hydraulic jump is a common phenomenon downstream of hydraulic structures that increases the flow depth by rapidly converting the flow from supercritical to subcritical and plays an important role in influencing hydraulic parameters. Examining previous studies on stenosis with natural wall roughness, what is certain is that no laboratory and numerical studies have been observed so far.

A laboratory flume with a rectangular cross-section 5 meters long, 0.3 meters wide, 0.5 meters high, and with Plexiglas floors and walls was used to perform the experiments. Two pumps each with a capacity of 450 liters per minute enter the flow into the flume and the flow inlet flow is read by two rotameters with an error of ± 2%. A point gauge with an accuracy of one millimeter was used to measure the water depth, and a construction meter with an accuracy of one millimeter was used to measure the length of the jump length. To create narrowing in the cross section of the channel from glass boxes with a fixed height of 0.5 m, widths of 2.5, 5, 7.5 cm on each side and to create supercritical current upstream of the section Narrowing A valve with a width of 0.3 m, a thickness of 3 mm with an opening of 2 cm, which is located at a distance of 1.5 m from the narrowing, has been used.Figure 1, schematic of the canal and the equipment installed on it and Figure 2, an example of stiffening placement, hydraulic jump formed in the flow path and rough placement method with three average diameters of 2.08, 1.28, 0.8 Shows centimeters on the wall.

In order to achieve the objectives of the present study, flow path constrictions have been provided using glass boxes and sand materials have been used to roughen the constriction walls. In total, 270 experiments were performed in the range of Froude number 2.5 to 7.5 and relative contraction range of 8.9 to 12.42. By adjusting the laboratory model and opening the pump, the flow enters the channel supercritically after passing through the vertical valve and moves towards the narrowing section.As the downstream Froude number increases, the relative energy dissipation increases and this amount is greater than the energy dissipation in the constriction of 15 cm. The reason for this is that due to the collision of supercritical flow with the constriction section, the backwater profile at the point of water collision with the sides of the constriction elements and also the formation of hydraulic jump upstream of the constriction section increase turbulence and climate interference and consequently it increases the relative energy dissipation.Changing the diameter of the rough particles has little effect on the amount of flow energy dissipation. But it can be seen that the effect of roughness with an average diameter of 1.28 cm is slightly more than other roughnesses. The reason for this is that the roughness of 1.28 cm has more contact surface with the flow and also the empty space between the grains increases the surface tension and shear stress. Therefore, some of the energy is wasted by hydraulic jumping and some of it is consumed by the backflow of the flow.

Comparison of the models with each other as a control showed that with increasing the amount of narrowing of the channel width, the relative energy consumption increases. According to laboratory results, the use of roughness significantly increases the relative energy consumption relative to the upstream. Energy dissipation in 15 cm constriction is 25.48%, 20.88% and 23.83% less than 0.8, 1.28 and 2.08 cm roughnesses in control mode, respectively. Energy dissipation in 10 cm constriction is less than 44.34, 43.68, and 40.63% in roughness compared to 0.8, 1.28, and 2.08 cm roughnesses, respectively. Energy dissipation at 5 cm constriction is 50.75, 51.19, and 40% less than 0.8, 1.28, and 2.08 cm roughnesses in control mode, respectively.

Due to the height of the dams, water behind dams have high energy and velocity on the spillway is high. Downstream of the spillway as a result of high energy and velocity of water on the spillway, is at the risk of cavitation and damage. The study of cavitation is crucial in this respect, and indicates the amount of flow degradation in the structure. Various works have been conducted on how to eliminate cavitation. Given the nature of cavitation, caused by high speed and pressure reduction, the use of roughness in parts of the spillway can help reduce or eliminate this phenomenon. This study aimed at investigating the effect of roughness under different conditions on changes in cavitation index in the downstream peak body.

To achieve a better understanding of how roughness functions, this research was carried out by changing its arrangement, number and different heights on the cavitation index using a laboratory model. In order to achieve a more real-life simulation, a spillway was installed at a distance of 5.5 m from the opening of the canal to ensure the flow is expanded and that the turbulence of incoming current is minimized. Peak spillway was considered in the study, designed and constructed according to USBR standards. Eight holes were installed on the spillway which were connected to 8 piezometers located in the channel body through flexible pipes to read the amount of pressure static. Effective parameters were identified with dimensional analysis, and three parameters (roughness arrangement, number of roughnesses, effective height of roughness) were tested. The roughness used in this research is made of PVC. After installing the spillway in the canal, the roughness was installed on the spillway. The piezometers were ventilated before each experiment. The channel slope was adjusted. Then, the pump was turned on, and after adjusting the flow rate, the test began. The depth gauge was calibrated for each aperture to measure and correct the height on the apertures. The equivalent pressure height inside the piezometer tubes was read and adjusted for the piezometer base and channel slope. Finally, according to the data, the roughness performance was evaluated using the cavitation index.

The experiments of the present study were performed with different Froude numbers and slopes. After the control experiments, the experiments were evaluated in three modes: the effect of arrangement, number and effective height.• Evaluation of cavitation index changes in control experiments:Observations show that cavitation index decreases as water falls on the spillway. The minimum cavitation index in the control experiment occurs at point 8. Moreover, the average cavitation index increases compared to the control mode by placing the roughness.• Investigation of roughness arrangement on the cavitation index:Observations show that the placement of roughness with convergent, divergent and row arrangement increase the cavitation index compared to the control. In the Froude number of 1.08, the changes in the cavitation index range from 1 to 8, 3.7, 4, 4.2, 4.4, 4, 3.7, 3.8 and 3.5%, respectively, compared to the case. • The number of roughnesses on the cavitation index:By placing 9, 12, 15 and 18 roughnesses in the row arrangement, the observations showed that in all graphs, the cavitation index increased compared to the control. Moreover, with the number of roughness, the cavitation index has a slight increasing trend. With 18 roughnesses in the flow rate of 1.08, the increase in the percentage of cavitation index (compared to the control) was piezometric points 1 to 8, 11.1, 4.03, 12.3, 17.6, 4.4, 4, 3.7 and 7.1.• Investigation of effective roughness height on the cavitation index:Considering the three effective heights of roughness, the observations showed that in all three cases, there is an increase in the cavitation index compared to the control mode, and the most evident change in the effective height has occurred at 0.017. With 1.08% increase in the flow rate of cavitation index compared to the control condition, 1 to 8, 7.5, 4, 12.7, 26.9, 4.1, 3.8, 7.3 and 6, respectively were obtained.

In general, it can be concluded that the installation of roughness on the spillway, the effective height of roughness, the number of roughnesses and its various arrangements, increase the cavitation index compared to the control. The presence of roughness reduces the flow velocity and increases the pressure on the spillway. This issue has a key role to play in eliminating or mitigating the cavitation phenomenon on the spillway. Compared to the control, the average cavitation index increased by 15.17% in the convergent arrangement, 11.8% in the divergent arrangement and 16.11% in the row arrangement. The results show that the greatest change in row arrangement and effective height occurs at 0.017 and n = 18.

Today, roads are considered among the main assets of each country so there is a need for a specific mechanism for their preservation and maintenance. Hence, the pavement management system, as an effective tool for decision-making and identifying effective and economical strategies, is used in pavement evaluation and treatment and also in maintaining roads in acceptable levels. In order to implement this system, having access to accurate measurement of different pavement indices, is vital. The goal of this study is identifying the effect of pavement distresses on the roughness and establishing a correlation between the two parameters to be used for evaluating the International Roughness Index (IRI) and roughness growth rate. In order to do this, using the Laser Crack Measurement System (LCMS), the roughness index and pavement distresses are measured in 10-meter length sections with lateral resolution of 1mm in several arterial roads of Iran. After the preliminary analyze of the LCMS output, pavement distresses with higher impact on roughness were identified and then, using artificial neural network (ANN), a correlation was established between IRI and pavement distresses. The relationship showed a correlation coefficient of 0.70. Putting this model into use, is a low-cost approach for road agencies to evaluate the roughness index as well as the roughness growth rate based on pavement distresses in network level. This in part would lead to better policy making and more efficient maintenance and treatment activities.

Studies show that of all petroleum products, a significant share (about 30%) is allocated to gasoline consumption; therefore, proper management of vehicle fuel consumption can have positive effects on economic and environmental aspects. In the present study, in order to investigate the effect of the pavement roughness and the longitudinal slope on fuel consumption, the pavement roughness and the longitudinal slope of three freeways including Tehran-Saveh, Tehran-Karaj and Tehran-Qom freeways, were measured in one hundred sections using a road surface profiler. Furthermore, by installing a Bluetooth diagram on the test vehicle, the amount of the fuel consumption was recorded for each section. Statistical analysis of the data showed that the pavement roughness and the longitudinal slope increase the vehicle fuel consumption significantly. In this study, an equation was proposed to predict the fuel consumption of the vehicles on freeways. According to the proposed equation, Fuel consumption increases 2 percent when International roughness index increases 1m/km.

Estimating the roughness of erodible open channels plays an important role in their hydraulic design. This parameter is important for the development of numerical models and hydraulic design of these erodible channels. For this reason, several empirical methods have been presented so far to estimate the roughness coefficient while the previous study shows that these methods are not sufficiently accurate. These methods usually are based on empirical activities which are too time-consuming and expensive. Therefore, in this paper, the so-called Artificial Neural Networks (ANNs) and Adaptive Network Based Fuzzy Inference System (ANFIS) methods as soft computing methods are used to estimate the roughness coefficient in erodible open channels. To achieve this firstly, it is attempted effective parameter on the coefficient are extracted based on empirical methods and a dimensional analysis. Then effectiveness of the parameters on the coefficient is investigated via a sensitivity analysis versus the error of estimation. Following to the development of the models, they are implemented to estimate the coefficient. Based on the method none-dimensional water depth, Sheilds number, shear Reynolds number and none dimensional falling velocity are determined as input parameters of soft-computing models. Final results show that the employed methods are more accurate than empirical methods to estimate the parameter and these methods can be used as an alternative method for the estimation of parameters. In addition, the effectiveness of some other parameters such as shear Reynolds number and none dimensional water depth over the event are extracted by the sensitivity analysis.

Due to the complexities associated with the determination of bearing capacity coefficient Nγ, researchers have proposed different values for this coefficient. As the roughness of foundation influences the value of this parameter, it is essential to consider its effect on Nγ. In the present research, the values of bearing capacity factor Nγ, has been determined by lower bound finite element method. The problem has been solved for a two-dimensional domain of the soil beneath a strip foundation. The domain was discretized into a three-nodded linear triangular element. In this method, in contrast to the conventional finite element analyses, the primary variables are three components of two-dimensional stress matrix. Differential equations of stress equilibrium in horizontal and vertical directions are the governing equations of problem. The bearing capacity is defined as the maximum load which can be applied to the foundation while not violating the stress constraints. The constraints include stress discontinuity and yield condition constraints. The stress components at a node common in adjacent elements are not essentially equal. The stress at adjacent element can be discontinuous. The condition of stress discontinuity means that the stress components should be such that the tangential and normal forces at common border lines of adjacent elements are in equilibrium. Moreover, the stress components should be such that they do not violate the Mohr-Coulomb failure criterion. The failure criterion was linearized into definite linear segments. The aforementioned equality and non-equality conditions construct a set of linear equations. The maximum load can be applied to the foundation was determined by linear programming as an optimization technique. The Nγ factor was calculated at two conditions of rough and smooth conditions. For the smooth foundation, an additional constraint was applied. The horizontal at the soil-foundation interface was imposed zero. The values of Nγ were compared at different values of soil friction angles. The values of the factor obtained from the current research were compared with the results of other relevant researchers including the results obtained from limit equilibrium, slip line method, upper bound solutions and lower bound solutions. The results indicate that the roughness of foundation affects the value of Nγ factor and consequently affect the bearing capacity. Therefore, in order to calculate the precise and reliable bearing capacity of a foundation, it is essential to take the effect of foundation roughness into account. The results of comparisons with the relevant studies indicate that the results of different methods do not differ substantially for the friction angles less than 30 degrees. On the other hand, the values of factors obtained from different methods differ substantially from each other for the friction angles higher than 30 degrees. This divergence increases by increasing the friction angle. The factors obtained from upper bound solutions are essentially higher than those obtained from the present research which is a lower bound solution. As the exact solution is higher than what obtained from lower bound solution, it could be stated that the reliability index of the factors obtained from the current study is higher than other methods. It could be concluded that the proposed factors can be regarded as a safe estimate for Nγ factor.

One of the most important phenomena in the nature with many undesirable effects for the environment is density current. Density or gravity current is a flow with a density of , which is higher than the ambient fluid with density of . This density difference causes a reduction in gravity g in the form of ). A schematic figure of a density current is shown in Fig. 1.

The bearing capacity of piles shaft and stability of retaining walls and reinforced soil structures depend on the behavior of soil-structure interfaces. Using direct shear apparatus، behavior of a sand with fine angular grains was studied. Steel plates with two surface roughness values were separately embedded at the lower half of the shear box and consequently، the upper half was filled with dense or loose sand. Then، the behavior of interfaces forming between dense/loose sand and rough/medium rough steel plates was studied. Tests show that the shear strength and dilation in sand-structure interfaces are significantly less than the corresponding values for sand. In this regard، the peak friction angle of rough steel plate in contact with dense and loose samples is، respectively، about 40 and 25 percent less than those of dense and loose sand. In a similar fashion، the peak friction angle of medium rough steel plate in contact with dense and loose samples is about 60 and 45 percent less than those in dense and loose sand، respectively.

Many investigations have been performed in order to increase the efficiency of energy dissipation over the spillways. In this study, the chute was roughened by means of the dentate blocks that were made of Teflon with new geometric shape and configurations. The experiments were carried out at three slopes, under six discharges and five dentate blocks configurations. Based on the laboratory results, it was concluded that the roughness geometry influences the relative energy loss. It was also found that using mix arrangements and selecting different sizes among roughness elements can increase the value of relative energy loss. Finally, it was observed that the dentate blocks spillway caused an extra 21% reduction in energy dissipation compared to the stepped spillway which is widely utilized to dissipate the energy.

Bridge pier scour occur due to down-flow and flow redirecting after it impinges the pier. Any increase or decrease of the strength of such flow can result in the decrease or increase of the scour depth. The present study showed that roughness can decrease the down flow strength and thereby the scour depth. This result was concluded through laboratory experiments. The results of experiments under different roughness dimensions and flow conditions are also

In this paper the experimental study of the flow pattern around a round wall jet has been carried out to investigate the effect of the bed roughness on the turbulence characteristics، including Reynolds stress and turbulence intensities. Measurements were conducted using the three-dimensional velocimeter، ADV and time series of the velocity components are used to investigate the variation of the turbulent flow parameters along the measuring domain. The results showed that by increasing the bed roughness، the streamwise and vertical turbulence intensities increase by downstream distance and for a specific bed roughness the streamwise turbulence intensity is higher than the vertical one. Furthermore، by going downstream from the jet entrance the bed shear stress reduces and by increasing the bed roughness، the bed shear stress has an increasing trend along the jet centerline. Location of the maximum bed shear stress does not change by changing the bed roughness.

Regarding necessity the scientific and clear criteria utilization for evaluating environmental costs, this research estimated a stochastic output distance function by measuring the environmental pollution parameters via analyzing in the transportation sector, as well as collecting the survey inputs and outputs production data. According to the Pigou’s theory which says each polluter should pay the costs of its pollution, given the lack of appropriate analytical methods for environmental policymaking, in this paper we made an estimate of shadow prices for environmental pollutions resulting from fossil fuel consumption in transportation sector. Accordingly, the average shadow prices in the transportation sector during the period of time from 1357 to 1389 for pollutants including nitrogen oxides (NOx) is equal to -121469.7 rials per ton-kilometer, sulfur dioxide (SO2) is equal to -131936.9 rials per ton-kilometer and for carbon dioxide (CO2) is equal to -488.4381 rials per ton-kilometer. These results suggested as a basic measure for planning to environmental policymakers to have a better knowledge of related economical-environmental effects of transportation sector and environmental costs.

Rock mass behavior is closely depends on rock joints characteristics, rock joint behavior is depends on its surfaces roughness. There are several methods to measure joint surfaces roughness by two or three dimensional. Three dimensional methods are expensive and advanced technology, thus to obtain high precision roughness of joint surfaces a new apparatus is designed and developed for first time in Iran. Using the designed apparatus the joint surfaces measurement with high precision is possible with low expenses. The apparatus is made up of two parts consisting hardware and software. Hardware consists of: laser head, cross table, and digital camera. The measured data is processed in software to obtain three dimensional surfaces roughness. As an advantageous of the developed apparatus it is possible to determine surface roughness using non-destructive method and same sample could be used for mechanical laboratory testing. To verify the apparatus performance a rock joint specimen roughness profiles is measured with 1mm intervals and the surface topography of joint surface is obtained with 1mm*1mm cell size. In this paper the apparatus assembly and its application along with the results are illustrated.

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