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Surface and Subsurface Flow through Block Ramps
No full textBlock ramps are permeable hydraulic structures. Flow that enters the block ramp infiltrates between the blocks and eventually on the porous base material on which the ramp is posed. The percentage rate of subsurface flow with respect to the total flow at the entrance of a block ramp or a rock chute is studied experimentally and analyzed by means of dimensional analysis. This quantity is described as a function of related parameters, such as the total inflow discharge, the particles' characteristics, the thickness of the base material bed, the geometric characteristics of the block ramp, and the boundary conditions at the toe of the ramp itself. The experimental data were elaborated in order to supply new formulations of the flow discharge through the base ramp material and the block ramp energy dissipation. The amount of energy losses of such structures is essentially a function of the geometry and the bed surface characteristics of the ramp, the hydraulic conditions, and the percentage rate of the subsurface flow
Indagini propedeutiche idraulico-geomorfologiche finalizzate alla manutenzione dei corsi d’acqua: il caso studio del Fiume Fine
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Sediment Transport on Block Ramp: Filling and Energy Recovery
No full textThe 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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