Research On The Hazard By Seawater Intrusion To Subway Line One Tunnel Structure And Comprehensive Measures

Subway is generally built below the water table, especially in the seriously eroded areas, how to solve the water corrosion of the underground railroad, has always been a major problem in the engineering sector. There are various reasons accounting for that. Underground waterproof and anticorrosive project is systematic, each link can affect the quality of the subway tunnel. Only by studying the construction technology systematically, calculating the tunnel water inflow correctly, and identifying a reasonable solution to waterproof anti-corrosive measure to the subway tunnel, can the safe operation of the subway be ensured.In this thesis, the influence of permeability coefficient and the thickness of grouting circle on the tunnel water inflow, and the impact of seawater intrusion on the subway tunnel structure are investigated from theoretical and numerical analysis based on the Nanguanling station in Dalian Subway Line test project, therefore the engineering solutions are proposed.The relationship between permeability coefficient and the ring thickness of grouting circle and tunnel inflow is reached by theoretical derivation and numerical analysis. And the analysis shows that the small penetration coefficient of grouting circle and the great the thickness of the grouting circle tends to decline the tunnel water inflow, but it doesn’t mean that the greater the grouting ring thickness and the smaller permeability coefficient are more favorable for the tunnel waterproofing. Depending on the circumstances, it is reasonable to combine with project-related information to select the parameters.In indoor trials, by comparing different physical characteristics of the grouting material, analyzing the advantages and disadvantages of various grouting materials from theory, and combining with the geology conditions of Dalian subway line Nanguanling engineering, the grouting materials for tunnel construction are selected.With the example and the establishment of two-dimensional, three-dimensional groundwater seepage numerical model, it can be reached that improving permeability coefficient of grouting circle can significantly reduce the water seepage in tunneling. However, when permeability coefficient is about0.1m/d, the seepage caused by tunnel excavation will not significantly change. Besides, by analyzing changing pattern of groundwater head, water pore pressure, and flow velocity variation in different excavation steps, graphs of the relationship among them are reached. Total water head of the tunnel and the pore water pressure caused by tunnel excavation decreased significantly, especially in the invert and arch foot where the changing degree is the weak link in the construction process and it needs special attention, which can provide guidance for the construction.