Structural Stability and Filling Materials on Geotube Dams

The flat shape of geotube which is used to construct dam for reservoir for fresh water supply at estuary in China is different from round shape of that in Europe and America on stability. The unstable model of the former is sliding, while that of the latter is overturning. The stability of geotube dam with modeled length scale of 30 is studied by wave experiment in a flume. The archetypal heights of model are 6.6m, 7.8m, 8.4m, 9.0m and 10.8m with slope ratios of 1.0, 1.25, 1.5, 2.0, 2.5 and the geotube dams are subject to regular wave by using constant wave steepness of 1/15, 1/20 and 1/25. Wave pressure in front of dam and up pressure at bottom of geotube affected by wave height, wave steepness, and overtopping are studied and the critical wave heights when geotube dams are unstable are obtained under different conditions. The formula of wave pressure in front of dam without overtopping is given by regressing. On the other hand, site experiments of eighteen geotubes filled with slurry of sludge clay, silt and fine sand from nearby area are performed at estuary of the Yangtze River. The results of observation on total pressure and pore water pressure show process of dewatering and consolidation of geotube with fine sand filling is suitable to geotube filling under tide condition at site. According to experiment and analysis, the dam of 9.9m high has constructed on the foundation of slurry clay to form reservoir of 3.56 x 106 m³ at estuary of the Yangtze River.