Zhoutouzui Immersed Tunnel Works In Guangzhou City Research On The Foundation Treatment On Variable Cross-section Works Of The Immersed Tunnel Section

Guangzhou Zhoutouzui immersed tunnel work is composed of foursections, including E1, E2, E3and E4. E1a nd4are designed as variablecross-section, and E2and E3is uniform cross-section. At present,variable cross-section tube is the first work in china, also rarely reportedaboard. According to the variable cross section’s pipe water pressuredistribution, pressure distribution, plate bottom sand pit development,alluvial sand plate development radius and sand plate density, we need toknow the design pattern of pressure sand hole in variable cross section isreasonable or not, and the find out the influen ce of the development ofsand disc radius factors.This subject is research on the sand replacement model test, which istaken in tube joints between at uniform cross section and variablecross-section, using the concrete bottom plate and water pool as1:1fullscale model for testing. The research analyzed various parameters thatwould effect the settlement of immersed tunnel foundation by using sandflow method on four points of view. They are the effect of sandpercentage on single hole test, the effect of clearance height of modelplate on single hole, the effect of the exited sand on single hole, the effectof model plate smoothness on single hole.The research result is that higher proportion between sand and water(1:8~1:9), can make the sand plate development faster and more uniform.The shape of sand plate can full of model plate’s bottom, which can reachthe design requirements of the750cm. In the pump pressure rangeallowance, we can select a higher sand water proportion that can be speedup construction progress. The smaller gap height will affect thebalanced development of the sand plate; but it had little effect on adjacentsand flow hole. Out of2.0m in the distribution of water pressure will haveobviously influence, but has little influen ce on the peak of water pressure. In the case of the both sides of sand plate, the angle of plate can also befilled with smooth, which is conducive to the balanced on the sand plate’sdevelopment.In the process of sand replacement test method, the develo pment ofsand plate in each direction of available cross-section is not completelysymmetrical. It should keep more sand as much as possible. When thetube section is lifted up by sand plate, it will seriously affect thedevelopment of sand plate’s radius; it has to strictly control pipe sectionin the construction process not greatly lifted up. In the process of tunnelconstruction, we cannot rely too much on monitoring the water pressureto reflect the tube whether it start s to rise.