Theoretical And Applied Study On Rainfall Factor Of Freeway Side Slope Soil Loss Model In Hubei Province

Soil loss is one of the most serious entironment problems in many countries including China. Construction project is an important manner resulting in soil loss besides agricultural reclamation and felling trees, which impacts the cost and feasibility of the project. In particular, freeway construction is of huge construction engineering with the characteristics of large earth cutting and discarded soil with wide distribution on working sites which will bring mass soil loss and beget sever harm in condition of poor defense. So, the freeway side slope soil loss model is researched in the paper, which will enhance the accuracy of soil loss forecast and provide the supervisor department scientific gist in freeway supervisor and maintenance.USLE is the most extensive use equation in soil loss forecast by now. But it is constructed based on the data concerning the two-thirds eastern areas of American and is restricted to cultivable slope (generally 0-7 degree) and low smectite soil. It will produce falsity if the equation is applied disengaging the original test area. Moreover, the equation was mainly used in agricultural programming and forecasting and the application in construction project has never appeared in report. In the paper the feasibility of the main influence factor, namely rainfall erosive index(R) in application to soil loss of freeway and rainfall are discussed in detail.The research is based on the Suizhou stretch of Xiaogan-Xiangfan freeway. Three different test spots are constructed and one auto pluvioscope is installed to collect detailed rainfall and soil loss data from April to December, 2004. One dimensional regression equation between soil loss and rainfall data is established with mathematical statistics method handling the advanced statistic software Origin 7.0 and Excel 2000. Research shows that the calculation model R= ∑E · I30 in USLE is also suitable for side slope soil loss amount of freeway and the calculation method for ∑ E is determined.Since the calculation of ∑E is fussy, the reduced calculation is researched which has greatly enhanced the monitoring and forecast efficiency. In this work,the relation between the total kinetic energy of rainfall ∑ E and moment maximal kinetic energy Ei, ∑ E and rainfall amount Pi, R and Pi are analyzed and corresponding equation is obtained. Research also found that the calculation cannot count the rainfall amount only when calculating soil loss amount in Suizhou section of Xiaogan-Xiangfan freeway.The principle for set sampling sites and sampling rates for side slope soil loss is implemented among the analysis of the relations, among rainfall classification, rainfall time ranges and soil loss amount combining by the monitoring method in this research. It has considerable practicability in freeway side slope soil loss monitoring and forecast.