Experimental Study on Automatic Opening and Restraint of Closed Stream-Mouth in a Coastal Conduit

Effects of layered structure

Abstract

In agricultural drainage systems, a coastal closed conduit structure has been frequently used as a method for solving problems related to river-mouths. In this paper, an effective improvement of the closed conduit structure is proposed on the basis of the results of the experiments described below.
Experiments
Several hydraulic phenomena, which occur when coastal sediment plugs are opened automatically by a stream, were investigated experimentally. The phenomena were affected by the critical velocity which prevents ocean waves from going upstream, the process of the automatic opening of coastal sediment plugs, and the influences of the wave and tide level on the automatic opening process.
Improvement Method
Taking the above experimental results into consideration, the layered structure was chosen as being an improved structure for the closed conduit. It was confirmed experimentally that the layered strucure has the following effects: 1) perfect sand flushing at the conduit bottom, 2) the control of the rise of the water level in the conduit, 3) the suppression of the wave progress into the conduit, and 4) the restraint of the closed stream-mouth.