基于WEPP模型的工程建设中施工便道边坡水土流失特征——以林芝市巴宜区为例

Soil and Water Loss Characteristics of Construction Service Road Hillside in Engineering Construction Based on WEPP Model-Take Bayi District,Nyingchi City as An Example

工程建设中施工便道导致的水土流失与传统土壤侵蚀不同,施工便道改变原自然坡面形态及水文过程,致使植被破坏、地表裸露,并形成路面、挖填边坡等多个侵蚀产沙部位,结构松散的路堑及边坡对降雨的响应更强、速度更快,土质低等级道路所引起的土壤侵蚀问题占比很大,因此研究可为工程扰动中施工便道的水土流失防治提供基础依据。以林芝市巴宜区为研究对象,采用WEPP模型对工程扰动下不同降雨条件、不同坡度坡长情况下施工便道边坡径流量、土壤流失量进行模拟分析,揭示施工便道边坡水土流失特征规律和关键影响因素。结果表明:(1)开始产生径流的60 min最大雨强(I_(60))为11.16 mm/h,降雨量为12.40 mm;I_(60)处于10~17 mm/h范围内径流量低于0.50 mm,土壤流失量低于0.010 kg/m^(2),当I_(60)超过17 mm/h后,I_(60)与径流量、土壤流失量具有线性关系。(2)径流量随坡度增加呈“快速增加—增速减慢—逐渐减小”3个阶段,坡度在5°以下时产生最低径流量56.98~58.00 mm,坡度在30°~35°时产生最高径流量76.19~77.01 mm;土壤流失量随坡度增加呈“先快速增加—后趋于稳定”2个阶段,坡度在5°以下边坡土壤流失量最小,坡度在50°后趋于稳定。(3)靠山边坡径流量随坡长增加而降低,不靠山边坡径流量则随坡长变化保持稳定,坡长在50 m后靠山边坡径流量低于不靠山边坡,且差异随坡长的增加而增大;靠山边坡土壤流失量随坡长的增加呈“先快速增加—后增速减小”趋势,不靠山边坡土壤流失量随坡长的增加基本保持匀速增加。研究结果用于高寒区工程扰动后边坡水土流失驱动机制分析。

The soil and water loss caused by the construction service road in engineering construction is different from the traditional soil erosion.The construction service road changes the original natural slope morphology and hydrological process,resulting in vegetation destruction,surface exposure,and has formed road surface,excavating and filling slope and other erosion and sand production sites.The road cut and slope of side with loose structure have stronger and faster response to rainfall.Soil erosion caused by soil low grade roads accounts for a large proportion,so the study provides a basis for the prevention and control of soil erosion in the construction of roadways.Taking Bayi District,Nyingchi City,as the research object,using WEPP model to simulate and analyze the runoff and soil loss of under different precipitation conditions,different slope and slope length under engineering disturbance,so as to reveal the characteristics and key influencing factors of water and soil loss.The results showed that:(1)When the maximum rain intensity in 60 min(I_(60))was 11.16 mm/h and the rainfall was 12.40 mm,runoff began to occur;When I 60 was in the range of 10 to 17 mm/h,the runoff was less than 0.50 mm,and the soil loss was less than 0.010 kg/m^(2).When I_(60)was more than 17 mm/h,I 60 had a linear relationship with the runoff and soil loss.(2)The runoff presented three stages of“rapid increase-slow down-gradual decrease”with the increase of slope.The lowest runoff was 56.98 to 58.00 mm when the slope was 5°,and the highest runoff was 76.19 to 77.01 mm when the slope was 30°to 35°.Soil loss presented two stages of“first rapid increase and then stable”with the increase of slope.When the slope was below 5°,the amount of soil and water loss was small,and the slope became stable after 50°.(3)With the increase of slope length,the runoff of backer slope decreases,while the runoff of non-backer slope remains stable.The runoff of backer slope was lower than that of non-backer slope after 50 m slope length,and the difference increases with the increase of slope length;With the increase of slope length,the soil loss of the backer slope showed a trend of“first rapid increase and then decrease”,and the soil loss of the non-backer slope basically kept a uniform increase.The results can be used to analyze the driving mechanism of soil and water loss in slope after engineering disturbance in high and cold region.