Study On Hydraulic Characteristics Of Flexible Apron Erosion

The apron should have enough water permeability, in order to eliminate theosmotic pressure of the bottom; meanwhile the apron should also have certain flexibility,in order to adapt to the deformation of river bed, punching capacity should be matchedwith the velocity. There are several kinds of traditional structure of the apron, such asdui-shi apron、dry-laid stone apron、precast concrete apron. These forms of traditionalapron have the advantages of low cost and simple construction, But When thedownstream riverbed is incised, fine particles of sand is swept to the downstream andcause the damage of apron. Sheathed flexible apron of Concrete can adapt to thefoundation deformation better, and the seam has a good water permeability, so thestructure used in the apron can ensure the smooth connection of the apron and thedownstream river bed.This paper takes a project as the background and uses the method of both physicalmodel and numerical simulation to research. The hydraulic characteristics of flexibleapron and anti-erosion ability is researched by the case without a flexible apron, thecase with a flexible apron precast bottom without geotextile, the case with a damagedgeotextile, and the case with a flawless and perfect geotextile.The physical model of the normal section with a scale of1:33is used in theexperiment to simulate the2sluice gate (28.0m), a2.5meter-width pier in the middle ofthe two holes, and two1.25meter-width half pier in each side of the holes, and the totalwidth of the model is33m; the upstream scour trough above21m to the downstreamchannel following64M as simulation range of scour prevention.By combining the structured grid and unstructured grid numerical simulation,hydraulic characteristics of large-scale use of fluid dynamics software Fluent ondifferent flow into the sea gate diffuse section is the three-dimensional numericalsimulation, distribution of flow velocity, bottom apron hydraulic parameters areobtained. the calculated results with the hydraulic model test results were comparedwith the scheme with numerical analysis under the condition of simulation, the resultsare basically the same.Through the experiment we can find when the geotextile is perfect or partlydamaged the precast apron integrity is not easy to damage; when the geotextile of lower part of the flexible apron is badly damaged, the flexible apron may be damaged if sandin the bed is scoured by water flow. So the flexible apron meet to the requirements ofenergy dissipation, but should strictly control the quality of geotextile and prefabricatedparts, as well as the laying of the construction quality.