Integrated Modeling The Surface Water Environment In The Freshwater Lake Under High-Speed Rail Braidge Constrution

Railway is a large linear project.it plays an important role as important national infrastructure construction in the national economy. Nowadays, there are high-speed rail (HSR) services in more than 15 countries, and the network is still growing at a very fast pace in many more. High-speed railway construction located in relatively complex area in geography, natural environmental conditions. with longer duration, across the surface water bodies and other features, in the harsh construction environment, a variety of harmful factors is likely to cause water pollution. destruction of water bodies self-purification capacity even affect aquatic organisms and the ecological environment.Above all, lake has relatively closed sharp and slowed flow.it is affected strongly by the external factors, especially sensitive to environmental disturbances. As a milestone in the field of HSR, It is not only in the level of advanced HSR technology, but also in the environment-friendly construction. It acrosses the third largest freshwater lake in Taihu Lake watershed called Yangcheng Lake, an important water supply and and strategic reserve water resource which has five ecological functions,The proliferation of a semi-enclosed discharge, crab ecological farming and parental nurturing, lake wetland protection, open water germplasm resources conservation and proliferation of releasing five functions. Beijing to Shanghai HSR is also fitted for the new features of future HSR from UIC report.To protect the freshwater lakes diversity and to avoid environmental accident, to reduce the environmental risk, It is necessary to analyze the extent of impact in each construction schems.Integrated simulation methods are adopted to explore the flow field and SS concentration field.In this paper, according to the relative research at home and abroad and the situation of data collection, using the integrated simulation method to calibrate the numerous tributaries flow, analyzing lake topography, depth and model selection relationship; Two schemes:(1) double row cofferdam and (2) steel trestle are proposed according to its designing features, and both are simulated using the current model. The coefficient of determination (R-), an indicator of strength of relationship between the measured and simulated values, is used to evaluate the accuracy of model prediction. The value of R2 is 0.726 for the calibration period and 0.799 for the validation period. The statistical results suggest acceptable simulation performance of this hydrodynamic model. In addition, aquatic species are analyzed and evaluated during bridge construction period and after the removal of selected construction scheme, aquatic organisms and water quality relationships are discussed, and the further impaction for the typical crab in the lake bridge is also assessed.The accidental discharge could be avoided by double row cofferdam construction.The main contributions of this integrated simulation work are listed as follows:1. GIS software is adopted to process DEM images at Yangcheng Lake and the surrounding, geometric calculation and visualization of attribute values are used to analyze the lake topography, water depth and water area, in order to determine a two-dimensional model, make full use of graphics and digital information to improve the accuracy of simulation;2. Because of tributaries of Yang cheng Lake are numerous (more than 50), and hydrological data of tributaries is lacked,so open boundary conditions for the model parameters calibration is difficult, a GIS-based SWAT model is used to descripted sub-basin and watershed outlet division, then the total flow is calculated to validate the boundary conditions of the water body;3. The construction schedule and the simulation step is almost the same, including the large and small mileage status of segmented cofferdam construction, numbers of steel pipes, distances.4. Many years of meteorological data and water quality monitoring data are collected, the two types of statistical methods R2 and P-values are used to test the model between simulated and measured values for the process of calibration and validation period to fit the state;According to the research above, this paper has positive significance in protection of sensitive water bodies, espacially concluding the effective environmental technologies for complex option of route and long construction duration HSR project.