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Articles by E. Amiri-Tokaldany
Total Records ( 3 ) for E. Amiri-Tokaldany
  S.A. Mousavi , E. Amiri-Tokaldany and M.H. Davoudi
  In this research by conducting laboratory experiments along with dimensional analysis, we investigated the nondimensional sediment discharge capacity and critical hydraulic gradient in rockfill dams. Rockfill dams are a type of grade control structures used to protect river bed against fluvial erosion and also to stabilize the river banks by decreasing the bank height. One of the main issues on utilizing rockfill dams is to keep its permeability enough so that it could be able to pass the flow as well as the sediment load through its body during flooding, avoiding sediments resettlement inside the pores. In this regard, the design of rockfill dams should be carried out so that the available hydraulic gradient is always kept greater than the critical hydraulic gradient, which consequently results in transporting the sediment through the dam body. In this research, a relationship to estimate the critical hydraulic gradient to transport noncohesive sediment through rockfill dam body is introduced. We tested the new equation using a set of published data and we found MRE equal to 0.4%. Also, using laboratory data obtained from tests on a rectangular rockfill dam, performing dimensional analysis and using linear regression, an exponential relationship for the required discharge to transport the sediments through the body of rockfill dam is presented. When we tested the validity of exponential relationship, we found a good accuracy for the equation (MRE = 9.4%) indicating that the introduced relation predicts the nondimensional sediment transport capacity well.
  A. Samadi , M.H. Davoudi and E. Amiri-Tokaldany
  With regard to many ambiguities existed on different types of cantilever failure in composite riverbanks and field study problems of this type of bank erosion, this phenomenon is not widely considered by other researches. The aim of this research was to investigate the experimental study of cantilever failure using data obtained from a field study in eroded banks of Kordan River. For this purpose, we used two samples of susceptible soil which were eligible to form overhanging block in riverbanks, in physical model tests. The physical, chemical and mechanical characteristics of those samples were previously determined via various tests. Accordingly, a soil block with optimum moisture contents and different densities has artificially been formed and consequently, certain depths of block are undermined in certain time steps. Then, the stability of overhanging block was assessed in each step. Finally, the failure pattern and related mechanism of cantilever failure was provided based on continuous images taken from deformations of soil block. Experimental results show that at least for our laboratory study conditions, the dominant failure mechanism is a toppling and this finding is in accordance with overhanging failure pattern, observed in Kordan Riverbanks. Also, failure mechanism in Cohesive Soil (CL) was progressive and accompanied with tension crack development. But in Loess Material (ML), the failure mechanism was momentary and deformations in upper part of soil block were not observed.
  J. Mozaffari , E. Amiri-Tokaldany and K. Blanckaert
  Presence of strong secondary currents and their interaction with the topography of the channel bed in river bends have significant effects on the distribution of longitudinal and transverse velocity and consequently the shear stress across the width and length of a bend. Flow in river bends has been investigated by several researchers, resulted in introducing a variety of different equations for identifying the parameters of flow in river bends. However, the proposed equations do not provide a good solution especially in sharp bends. In this research, we carried out a set of laboratory tests to investigate the distribution of the longitudinal velocity in sharp river bends. The tests were performed in the laboratory of hydraulics department of EPFL University in Switzerland, with discharges of 63, 89 and 104 L sec-1 on a developed topography. Based on the test results, we presented an experimental equation includes two, a power and a sinuous, segments to estimate the longitudinal velocity in sharp river bends. Having determined the longitudinal velocity profile using the new model and also some available models, we calculated the Standard Error of the predicted against the observed results from laboratory experiments. We found that the Standard Error of the new model is considerably lower than the Standard Error of the other models, confirming the high accuracy of the new equation on predicting the longitudinal velocity profile in sharp bends.
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