Study On Random Model For Water Environment Simulation And Training On Closed Polders And Its Application

Vertical cut-off wall are often used to reinforce dikes for preventing seepage through bases when polder training is conducted. And usually the wall reaches to the aquifuge. This hydrotechnic can prevent dike base seepage effectively, decrease the piping, soil losing, soaking, dipping, swamping and other hidden troubles. But once the technique is adopted, the flow pathes of ground water will be truncated, and thus a new closed polder come into being. Here the ground water inside and outside of the polder can not exchange freely, so several years later, the dipping and swamping in the farmland may be aggravated. Meanwhile, the eluviating of the fertilizer, the pesticide and the salinity in the soil will result in the accumulation of contamination and even result in the deterioration of the quality of ground water, and bring bad influence to regional environment.In this dissertation, first, considering the groundwater regime in a closed polder is influenced by various factors(e.g. precipitation, evaporation, surface water, etc.), which determines that the groundwater regime bears periodicity, trend and randomicity; therefore, the corresponding random(time series) model is established for the above random factors by dint of random theory and time series theory. And then, by evaluating various boundary conditions synthetically, a universal random model for water environment simulation and training on closed polders is established. Advection, dispersion, sink/source and chemical reactions are discussed and studied carefully in this part. Next, the solution techniques and numerical implementation to the above universal random model is explored. Finally, the model established in this dissertation is applied to JIANGXI GANDONG polder. After calculation, simulation and analysis, the following results are educed: the vary trend of ground water level and ground water quality under different close rate in the studied area and feasible recharge of contaminations. The results will offer a guidance on the water conservancy engineering and the corresponding administration for the similar regions.At the end of this dissertation, conclusions and research tendency in the field of water environment simulation and training on closed polders is summarized briefly.