| Foundation treatment is one of the most important stages of immersed tunnel construction. Due to its advantages, the sand flow method has becomed the first choice of immersed tunnel foundation treatment on the hard ground and widely applied in engineering field. A successful foundation treatment can directly affect to the service and security immersed tube tunnel. Once the settlement exceeds the allowable value or differential settlement, regardless of size, the subsequent processing will be very difficult, even impossible process appears. Therefore, the mechanism and design method research on the sand flow method of immersed tube tunnel ground treatment are necessary, to ensure that the tube contact with basic solid, and have important engineering significance. In sand flow method process, the movement of sand depends mainly on the flow field as a transport, and in turn affects the fluid flow field. At the same time, few of the theoretical studies on foundation treatment were mentioned. Therefore, it is necessary to deal with the whole process of sand flow method from the theoretical point, to achieve optimal guiding purpose of construction.The related detection equipment was researched in this paper, which had solved the real time detection problem underwater experimental environment. A full scale model experiment system was designed, and comparative test about the changeable condation of sand-water ratio, foundation trench depth and boundary conditions were implemented, the detailed data was got. The two-phase flow theory was cited into this paper to research the mechanism of sand and water, calculated the mathematical model of sand and water flow, simulated the test process sand complemented the parameter studies of the sand flow method. This paper analysised the complex conditions influence in sand plate forming and applied to the construction of sand flow method by using processing method of the equivalent uniform fluid.The research conclusion of this paper mainly has the following several aspects:(1) Sand disc molding experience “accumulation” and “extension” two stages in sand flow method, sand particles experience the “rose”, “pipe” and “deposit” three process from injection to deposition.(2) The ideal sand-water ratio is 0.1 to 0.15 and the reasonable depth of foundation trench is 0.8 m to 1.0 m in sand flow construction. In the sand flow method, the sand-water ratio and the trench depth has a great influence on the sand disc of the axial develop, the characteristic of accumulation of sand flow, the size of impact crater, the flow seam and the water pressure in the trench.(3) When adopting sand flow method construct at a certain water velocity in the trench, it still can form sand disc, this boundary shape of sand disc characterize the curvature radius of the downstream boundary smaller and the curvature radius of the upstream boundary is larger.(4) The boundary impact on the proposed construction blasting holes reach a large area within a radius of 2.3m range from the vents. After the sand-deposit forming, the other side boundary of the sealing edge remains an arc.(5) Compared with parallel arrangement scheme, staggered arrangement of the sand disc with the higher degree of compactness and fullness. The design and construction principle of pipe sections sand-deposit is that the sand-deposit should be symmetrically arranged, as far as possible to ensure a large area of overlap sand-deposit, to avoid acute angle boundary in the sand-deposit construction process. |
PDF Full Text Request