Study On Forecast And Prevention Of Soil And Water Loss Of Expressway In Sichuan Mountian Area

The forecast of soil & water loss as the outpost of soil and water conservation is the base of preventing and controlling soil erosion through scientific way. At present, the forecasting methods and preventing countermeasures have being widely researched at home and abroad , but the ranges were mainly fastened on farmland and forest of large areas or drainages, so the reports about its application study that including the Expressway construction projects are few.The excavated slope of Ramp A of Huangshui Interchange and the left spoil area of K11+100-K11+210 of in the national road NO. 108 from Xichang to Pazhihua was selected as the object of field tests of soil and water loss, in this article. Three continuum test slopes were set up at the north side of the spoil field. The field rainfall and soil-water loss were measured form June to July, in 2003. The result show that volume weightiness of the sediment is1.46g/cm3, and loss volume weightiness is 1.51g/cm3; however the standard erosion rainfall to cause soil & water loss is about 6mm that less than the standard of ordinary slopes or agrarian slopes; and the turn gradient of the slope is about 38.4°to 43.0°among, which is bigger than ordinary slop and agrarian slopes' erosion turn gradient at 25°to 29°. While using the soil conservation bureau of USA's usually soil loss equation(USLE)as the forecast model, by observational record to make sure its two main parameters: 1 the most agreeable rainfall and steam erosion gene (R )is the average product values of soil loss, total raining power(E)and max. raining strength in 60mins(I₆₀),and the R is a monthly average value. 2 the erosion gene K is got by analogizing the observational datum of rainfall, in which slop gradient is 2.22t/ha,excavative gradient is0.57t/ha, spoil area top is 1.37t/ha.Flowed the forecast model to estimated values of slop gradient, spoil area top and area lost quantity in a single month, and then to compare with the tow main methods of accelerate erosion coefficient and flow discard ratio method to find that the accelerate erosion coefficient A at the present experience forecast model is tending to smaller, and the flow discard ratio value B at the popular flow discard ratio method reportes are tending to bigger. This study have clear reference value to soil erosion prediction on the Expressway, and play some guiding role on Soil and Water Conservation Work on expressway at the same time.