A Study On Immersion For Reservoir And The Analysis Of Drainage And Depressurization Inside Dikes

The immersion for reservoirs is a geological problem of reservoir environment. With the experiment and lessons from the effect of immersion on the ecosystem near the reservoir, the immersion has caused much attention. Taking the immersion in Xing Long Water conservancy project and Cui Jiaying shipping-dynamoelectric project in Hanjiang river as the background, the characteristics of immersion and methods for preventing immersion have been studied with the international popular software Visual Modflow to set up mathematics model on the basis of summarizing research results. The Modflow basic principle and inside structure were explained and the Drain, Recharge, Evapotranspiration and relief well boundary were illuminated in this thesis. The main content can be divided into three parts.First of all, the general mathematics model was established that was used to analyze the water table depth for two types of soil structure in the condition of different thickness of top layer, river level and depth of river bed. The immersion degree could be evaluated with the criterion of pre-defined critical water table depth and significative conclusions were drawn from the simulationSecondly, according to the immersion characteristics, the drainage effect and reasonable distance and depth of drainage ditches (including subsurface tube) were discussed to different soil structure with steady state flow. The relief well is commended when the hydraulic conductivity of top layer soil is less than 10^-6cm/s. Three dimensional steady state model was adopted to simulate the distance, the proportion of filter length and the elevation of well head. The relative rational control parameters of relief wells were gained through comparative analysis.At last, in term with the meteorological condition, geological condition of midstream and downstream of the Hanjiang River, a transient flow model was established to predict the distribution of water table and the immersion degree after the hoisting of river level,and In this course, the determination of recharge and evaporation coefficients were discussed in detail. These methods can serve for immersion analysis under the similar condition. The drainage and depressurization results of drainage ditches and relief wells were simulated with transient flow model, and the drainage efficiency was calculated by transferring Zone Budget module.In a word, the conclusions from the numerical simulation offer the reference suggestion for prevention and control of the immersion for reservoirs.