Study On The Test Of Stability Of Geotube Embankment During Construction

The technical of constructing embankments with filling geotubes is sophisticated enough oversea, the development of the technical is also great in our country, it is extensively used in coastal protection and reclamation engineering now. There is few criterion for us to obey in designing, we can only consult past experience in actual projects, so this aspect is studied in this paper because of these reasons.The stability of geotube embankment under wave and current action is studied in this paper. In this paper, regular wave, geometric scale of 1:35, two kinds of wave steepness of 1/20 and 1/25 are employed in the model test of wave. The model geotube embankments with top width of 15cm, heights of 12cm, 18cm, 24cm, and degrees of slope of 1.25, 1.5, 2.0,2.5 are employed. The principal contents of the study are as follows:(1) In the case of different water depth ahead of the embankment and different wave factors, the critical wave heights of embankments with different degrees of slope and heights of embankment, and influences between critical wave height and the water depth, wave steepness, degree of slope, height of embankment are studied.(2) Changes of wave pressure ahead of the embankment and uplift wave pressure subjected to the changes of wave height, wave steepness and degree of slope are studied. The formula of Soviet Russia of wave pressure on the slope of embankment with smooth armor is analyzed, and it is amended to make it suitable for the geotube embankment. Influence between uplift wave pressure and permeability of geotube, gap between geotubes are studied. Approximate methods of calculating wave pressure ahead of the embankment and uplift wave pressure of the top geotube are presented.(3) Modes of destabilization of geotube embankment (a layer or multi-layers of geotubes appear displacement when in destabilizing condition), influence between appearance of displacement of geotube and overtopping, uplift of geotube is studied. Also development of displacement under the continual wave action is studied.(4) Based on the wave pressure measured, the destabilizing conditions are checked and analyzed. The calculating formula of wave pressure on the top geotube is deduced by dimensional analysis, combining with the principle of limiting equilibrium, empirical formula of safety factor of the top geotube is founded.(5) The critical current velocity of geotube embankment under current action subjected to different heights of embankment and degrees of slope is studied. Influence between height of embankment, degree of slope and water depth over the embankment, current velocity near the top embankment in critical condition is studied, also the stability of geotube embankment subjected to these factors is analyzed. The results of this test are analyzed by the formula of critical current velocity concluded before, and the formula is amended too.