Research On Variational Section Immersed Tunnel Foundation Treatment Model Experiment

As one of the advanced method of immersed tunnel foundation treatment, sand flow method will be more used in our construction of immersed tunnel due to its low price, not impeding Navigation, and not be affected by some hydrological conditions such as the tide ,the depth and the velocity of water. In the national immersed tunnel, sand flow method was used in the Guangzhou Pearl River Tunnel, Shanghai outer ring immersed tube tunnel, and Guangzhou biological Island - University City Tunnel. Because each immersed tunnel has its particularity, the application of sand flow method needs to combine the existing construction experience and specific model experiment to determine a series of control indicators as a guide, such as the filling degree and the diffusion radius of the sand pancake, the sand flowing pressure.Sand flow method is used in the Guangzhou Zhoutouzui immerse tunnel which in under construction. Unlike the immerse tunnels which had been built in the country, it has variational section immersed tube. Base on experience of construction and model experiment, this paper the paper presents the research on variational section immersed tube. By means of 1:1 physical model experiment, the mechanism, diffusion rules, the sand flowing pressure and the compactness of sand pancake were analyzed. The main work includes:(1) Sums up the current foundation treatment methods of immersed tunnel and their advantages and disadvantages; compared and analyzed the model experiment in the nation;(2) According to the practical engineering requirement, in order to get close to the actual test parameters, a 1:1 model experiment on variational section immersed tube was designed, including equipment set up, site layout, test and the design of the experiment process;(3) Through the adjustment of sand water ratio, carried out three times specific sand-flowing experiment;(4) Comparing the test data of different sand ater ratio, the diffusion law of sand pancake in the variational section immersed tunnel was analyzed. And the sand-flowing pressure was analyzed too. It was further divided as bend pressure, pipe pressure and crater pressure.(5) Distribution laws of the compactness of sand pancake was analyzed.