| With the continuous increase of highway mileage and the rapid development of automototive industry,the environmental pollution caused by highway transportation is more and more got attentions of people. The runoff pollution of road surface is an important aspect of environmental pollution caused by transportation.Presently the road guid-drainage system devised with soil's self-purification can effectively reduce its impact. The paper does the experimental and theoretical research for the key technologies of Road's Guided-drainage System's and the characteristic of soil's self-purification,and acquires some useful conclusions.It provides the theoretical basis for the design of road drainage systems to more effectively reduced runoff pollution, and protect the surrounding ecological environment of roads.Firstly, this paper acquries the mechanism of its purification runoff pollutants, and carries out the soil column unit model test of the characteristics of the soil's self-purification based on the previous research results to discuss the mechanism of the soil self-purification characteristics, and combined with the structural features of guided-drainage systems.On this basis,the introduction of soil solute transport theory conducts the theoretical analysis for guided-drainage systems and carries out numerical simulation with HYDRUS series software,which includes soil column element numerical simulation and physical modeling simulation of guided-drainage systems.In the numerical simulation,it first verifies the reliability of the model HYDRUS-1D,then gets the comparing results between the simulated value and the measured value of ammonia in the second test the outlet with HYDRUS-1D.The comparing results shows the HYDRUS-1D model can better simulate soil solute transport process. Then it analyzes the impact of three main parameters(diffusion coefficient, absorption factor, the rate of reaction parameters) of solute transport on soil solute transport with HYDRUS-1D model.Finally,it simulates the solute transport process of guided-drainage systems with HYDRUS (2D/3D) program,then obtains the migration and transformation characteristics of solute in the guided-drainage systems,and analyzes the impacts of slope angle and slope length on the purification of the guided-drainage systems.The tests and theoretical results shows:①the type of soil is one of the main indicators affecting pollutant migration and transformation, the silty clay column (CODcr, NH4-N, TN) is better for the removal of pollutants than silt and sand column;②The removal rate of soil column group with cosmid for the NH4-N reached more than 58%,while the non-cosmid soil column group is less than 20%.The removal effect of clay on chemical oxygen demand and total nitrogen was relatively small.③While purifying effect of red soil for CODcr and TN increases with void ratio increasing,the effect of the void ratio conditions on the purification of NH4-N is small.④From the trend of change,the effect of the void ratio conditions on the purification of CODcr is large.⑤The impact of the first reaction parameters on water treatment concentration is maximum in three key parameters of solute transport,followed by absorption factor,diffusion coefficient is minimum;⑥The movement speed of solute along the direction of slope of the road guided-drainage system decreases,the closer to the top of slope,the greater the concentration of the solute peak,and the shorter the time to reach equilibrium;⑦The change of slope has no effect on the solute transport of guided-drainage system,the impact of slope length on the solute transport of guided-drainage system is maximum within a certain range,the impact is small after a certain value,which there is an optimum slope length values making the purification efficiency of guided-drainage system best.
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