Designing and construction methods of reinforced river dike in a natural environmentally friendly way

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In order to establish a design and construction method as a new application of the reinforced soil, river dike embankment method with geo-grid reinforcement is proposed. There are some uncertainties in the design concept of the reinforced soils used for the river dike. Such factors as the limitation of the length of geo-grid reinforcement in rive dike, the quality of filling material, the design river-water flow speed, the resistance of the front unit against floating logs and boulders, and the plantation on the dike surface for preventing soil draw-out, should be investigated. In this study, a real scale field construction and field monitoring were conducted to establish a design and construction method of the reinforced soil.At the first trial of real scale in situ test, some of the filling materials were drawn out from the dike. On the other hand, overall deformation process by scouring and surface deformation process by floating logs were observed at the real scale test on the field. Based on these test results and observed facts such as soil draw out and erosion of top surface at the very heavy rain, an improved river dike was reconstructed. In this test river dike, materials for soil draw out were improved and some improvements design were tested and various kind of measuring includes pore water pressure in the dike were conducted for two years. From this test results, the reinforced river dike was confirmed its performance and behave as a unit of one construction when it was constructed with reasonable method. Based on this research, a new design method for external stability and for evaluation method with flow of dike stability were proposed. It is proposed not only for dike on the land but also for river dike with new improve methods that includes effects of water level fluctuation in river and in the dike.