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RISS 인기검색어
- 검색키워드
- 저자 : Stefano Pagliara (검색결과 2 건)
- 무료
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Sediment Transport on Block Ramp: Filling and Energy Recovery
Stefano Pagliara,Michele Palermo,Ilaria Lotti 대한토목학회 2009 KSCE JOURNAL OF CIVIL ENGINEERING Vol.13 No.2
The effect of sediment transport on both morphology and energy dissipation in presence of non conventional stream rehabilitation structures, such as block ramps or rock chutes, is a not well explored topic on hydraulic engineering. Namely, in normal functioning conditions, these types of structures are generally located in mountain rivers, which are characterized by an elevated sediment transport which can be deposited and trapped between the rocks constituting the ramp. This causes a change in the bed roughness and in the energy dissipation process that is present on a block ramp. This occurrence was experimentally investigated at the Hydraulic Laboratory of the University of Pisa. Different experimental conditions were tested and the main hydraulic and geometric parameters controlling the filling phenomenon and its effects were highlighted. Namely, it was experimentally proved that both the median diameters of the filling material and of the ramp blocks, the ramp slope and the discharge are the most relevant parameters governing the ramp filling. Thus, experimental formulae were derived to foresee the ramp morphological changes and the interaction between the filling process and the geometric and hydraulic parameters. Moreover a comparison of the energy dissipation on block ramp was conducted and the energy recovery in presence and absence of filling material was compared. The effect of sediment transport on both morphology and energy dissipation in presence of non conventional stream rehabilitation structures, such as block ramps or rock chutes, is a not well explored topic on hydraulic engineering. Namely, in normal functioning conditions, these types of structures are generally located in mountain rivers, which are characterized by an elevated sediment transport which can be deposited and trapped between the rocks constituting the ramp. This causes a change in the bed roughness and in the energy dissipation process that is present on a block ramp. This occurrence was experimentally investigated at the Hydraulic Laboratory of the University of Pisa. Different experimental conditions were tested and the main hydraulic and geometric parameters controlling the filling phenomenon and its effects were highlighted. Namely, it was experimentally proved that both the median diameters of the filling material and of the ramp blocks, the ramp slope and the discharge are the most relevant parameters governing the ramp filling. Thus, experimental formulae were derived to foresee the ramp morphological changes and the interaction between the filling process and the geometric and hydraulic parameters. Moreover a comparison of the energy dissipation on block ramp was conducted and the energy recovery in presence and absence of filling material was compared.
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Study of Scour and Flow Patterns around Triangular-Shaped Spur Dikes
Mohammad Bahrami-Yarahmadi,Stefano Pagliara,Elham Yabarehpour,Noushin Najafi 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.11
River bank erosion can upset the balance of the river and its aquatic habitat, as well as the lands and facilities adjacent to the river. As hydraulic structures, spur dikes are constructed perpendicularly to erodible river banks in an attempt to divert the flow toward the middle of the channel as a measure for reducing and controlling river bank erosion. The expansion of the scour hole at the tip of the spur dike can lead to structure failure. Inclining the horizontal crest of the rectangular spur dikes (called triangular-shaped spur dike) can reduce the scouring at their tips. There are limitations on the design criteria for this newly-introduced structure. In the present study, the scour patterns developed around triangular spur dikes were examined under different hydraulic conditions and compared these patterns with those obtained for common type of spur dikes (rectangular spur dikes). The three-dimensional velocity components around triangular and rectangular spur dikes were also measured. According to the results, maximum scour hole depth and volume were smaller in the triangular spur dikes than in their rectangular counterparts. Quantitatively, on average, maximum scour hole depth and volume in the former were, respectively, 44% and 70% less than those in the latter. Based on the analyzed the flow patterns, it is recommended that the spacing between the triangular spur dikes should not exceed 5.5 times the effective length of the structure.
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