Structural Waterproofing And Drainage Technology Of Large Section Near Sea Tunnel

In the course of the construction on near sea tunnel, waterproof and drainage is the key factor to the safety on construction and operation of tunnel. Because of the characteristics and difficulties on near sea tunnel, waterproof and drainage technology is more and more attracted by the engineering circles. Take the Gongbei tunnel as the engineering background, based on theoretical analysis and laboratory test, study on the theory and technology of near sea tunnel. The main results are as follows:(1) Based on groundwater mechanics and complex variable methods, the analytical model of the near sea tunnel seepage field is established and the analytical formula for water inflow and water pressure distribution of near sea tunnel in uniform rock are derived. Using the hidden digging section of Gongbei near sea as engineering background, the seepage field of near sea tunnel is analyzed. The result shows that the permeability coefficient and thickness of the grouted ring, primary support have great influence on the water pressure at lining back and water inflow, safety factor.(2) Based on similar theory of model test, similar criterion is derived. The model test of near sea tunnel in stress field and seepage field is carried out on the test framework whose prototype is Gongbei near sea tunnel. The model test result shows that in the case of entire plugging the lining must support the full hydrostatic pore pressure and the water pressure can not be discounted. In case of limited drainage, the drainage system has a great influence on water pressure at lining back. Water pressure at lining back has an inverse liner proportion to the controlling water inflow of the near sea tunnel. The effect of water pressure discount is more obvious when the test point is closer to the drainage hole. With the increase of external water head, strain of deformation joint should become a linear increase. If drain from deformation joint, the water pressure will be reduced.(3) Analyzed the influencing factors of concrete self waterproofing performance on near sea tunnel, based on system of concrete mix design method. To carry out test of self waterproofing performance optimization design on different water cement ratio and admixtures. The results of the study show that in the benchmark with ratio based on single doped mass fraction on 20% fly ash, composite doped mass fraction on 20% fly ash and 10% of the slag can meet the requirements of engineering quality and relatively better. Then, the results show that the self waterproof performance of the composite with 20% of the fly ash and 10% of the slag concrete is the best. The results of the study can provide reference for the concrete mix ratio of structure on Gongbei tunnel lining.(4) Theoretical analysis and laboratory test method were applied to the optimization of the detail waterproof structure of near sea tunnel, which developed a new type of back-paste and drainage waterstop, buried and drainage waterstop. It could effectively improve the resistance to chemical corrosion on waterstop, when the waterstop’s EPDM material by adding into mass fraction of 5% graphite. By sealing with a high water pressure test, found limit value of resistant pressure on new back stick type water stop and embedded type water stop were 1.2MPa and 1.8MPa, which meet the need of near sea tunnel. According to the research results, the Gongbei tunnel deformation joint waterproof structure has been optimized. The side wall could set back-paste and drainage waterstop and the soleplate could set buried and drainage waterstop, which the water of side wall and the bottom water can be row guide effectively.(5) Deformation joint of near sea tunnel is a weak link of waterproof, use method of theoretical analysis and numerical calculation to optimize the deformation joint spacing on open excavation section of Gongbei tunnel. The research results show that the deformation joint spacing of the open excavation section should be adjusted to 100m, the optimized deformation number is 70, which reduce 42 and occupies compared 37.5%.