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

为了建立一种新的加筋土应用的设计和施工方法，提出了土工格栅加固河堤法。河堤加筋土的设计理念存在一定的不确定性。应考察河堤土工格栅加固长度的限制、填筑材料的质量、设计河水流速、前单元对浮木、浮石的阻力、防渗堤面上的种植等因素。本研究通过实际规模的现场施工和现场监测，建立了加筋土的设计和施工方法。在第一次实际规模的原位试验中，从堤防中抽取了一些填充物。另一方面，在现场进行了实尺试验，观察了冲刷变形的整体过程和浮木变形的表面过程。在此基础上，结合观测到的特大暴雨条件下的抽土、顶面侵蚀等情况，对改良后的河堤进行了改造。在该试验河堤中，对抽土材料进行了改进，进行了一些改进设计试验，并进行了两年的孔隙水压力等各种测量。试验结果表明，在合理的施工方法下，加固后的河堤具有良好的性能，是一个整体工程。在此基础上，提出了一种新的堤防外部稳定性设计方法和堤防流动稳定性评价方法。不仅对陆地堤防，而且对河流堤防提出了新的改进方法，包括河流和堤防水位波动的影响。

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.