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Articles by M.H. Davoudi
Total Records ( 4 ) for M.H. Davoudi
  M.H. Davoudi and E. Kabir
  In this research, the effect of sodium chloride on the soil strengthening by lime is examined by a series of laboratory tests. In the process of strengthening and stabilizing salty soils by lime, the naturally existing salt interferes in the lime-soil reactions which may result in either intensification or mitigation of the process result. CL-ML soil samples were mixed with 2, 4, 6 and 8% of lime and 1, 2, 3 and 5% of sodium chloride. After being compacted and cured for a period of 7 or 28 days, their resistances were measured by running uniaxial compressive test. The results reveal that the presence of sodium chloride in a soil-lime mixture improves the compressive strength of the mixture. This increase is due to an increase in pH of the media by sodium chloride and thus an increase in the dissolubility of silicates to interact with calcium and create pozzolanic process to produce cement. Also a calcium-sodium silicate gel improves the cementation faster than a calcium silicate gel. Also it was found that the positive effect of salt on lime-soil mixture resistance is more pronounced when the percentage of lime is low.
  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.
  A. Nazemi , L.T. Shui and M.H. Davoudi
  Recently pervious rockfill detention dam is used as a flood mitigating structure. Analysis of hydraulics of turbulent flow through this kind of dam is mostly done using Darcy-Weisbach equation. So far, many attempts have been made to study the friction coefficient as a function of Reynolds Number in turbulent flow of clean water through pervious rockfill detention dams, while this subject has remained intact for sediment laden flow of water. In this paper relationship between friction coefficient and Reynolds Number for sediment laden flow through highly pervious rockfill dams was investigated. Required data for a regression analysis obtained by conducting a series of laboratory tests to calibrate and validate a proposed power law friction coefficient-Reynolds Number relationship. A changeable bed slop Plexiglas flume, an adjustable rate sediment feeder and a recirculating flow electro pump system were used in present study. The tests were carried out on four different rectangular laboratory rockfill dams and three different non-cohesive suspended sediments. A power law relationship was obtained with a correlation coefficient of 0.74 using two thirds of laboratory measured friction coefficient and Reynolds Number. The obtained relationship was validated employing the remaining unused data with a Mean Square Error of 0.29 which is an acceptable agreement. A new power law relationship was found between friction coefficient and Reynolds Number in sediment laden flow through pervious rockfill dams. This new relationship is the only one thus has been proposed for the sediment laden flow of water through pervious rockfill dams.
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