Research On Soil Erosion Law Of Engineering Accumulation Slope Under Repetitive Runoff Scour Conditions

As a main source of sediment for newly added man-made soil erosion,engineering accumulation body will experience multiple erosion of rainfall and confluence under the actual climatic conditions in the wild,forming a large amount of eroded sediment.In this paper,the simulated engineering deposits located in the Yangling Soil and Water Conservation Field Scientific Experimental Station were taken as the research object.The test was carried out for the slopes of each engineering accumulation body in a quantity of 3 times by the method of runoff scour.The purpose is to explore the characteristics of slope erosion under the condition of multiple scouring of the upper confluence.The preliminary conclusions are as follows:(1)Under the test conditions(after the first water release scouring,when the soil moisture content on the slope surface drops to the initial water content,follow-up tests are conducted),The slope runoff rate showed an upward trend with the scouring duration.The average runoff rate of the first run was 8.501 L/min,and the latter field increased by 1.8% and 18.9% respectively compared with the previous field.The sediment yield on the slope showed a declining trend after the peak of scouring.The average sediment yield in the first game was 1.856 Kg/min,and the latter one decreased by 28.4% and 40.5% compared with the previous one respectively.The cumulative runoff and accumulated sand production on the slope have a quadratic function relationship with the erosion duration.The cumulative runoff increased significantly with the increase of the scouring field,and the cumulative sand production decreased with the increase of the scouring field.(2)Under the test conditions,the runoff velocity on the slope shows a downward trend with the erosion duration.The average velocity of the first field is 0.411 m/s,and the latter field decreases by 12.1% and 5.0 respectively compared with the previous field,the flow velocity on the slope shows a decreasing trend as the scouring field increases;The Reynolds number continued to increase as the scouring lasted.The average value of the first Reynolds number was 638.01,and the latter one increased by 79.6% and 39.8% compared with the previous one.The Froude number showed a downward trend as the scouring duration continued.The average Froude number of the first test was 4.325,and the latter field's value reduced by 38.3% and 25.9% compared with the previous filed,and with the increase of the number of test sessions,it shows a decreasing trend;The resistance coefficient,runoff shear force and runoff power of slope runoff show an increasing trend with the scouring duration.The average value of the above three parameters with the increase of the number of test sessions,all show the change trend of field 3> field 2> field 1,and with the increase in the number of test sessions,the average increase of the latter field is lower than that of the previous field.(3)Under the test conditions,the eroded sediment particles on the slope are mainly powder particles and sand particles,and the clay particles are the least.The average percentage of clay particles with the increase of scouring times was 0.922,0.824,0.704.The average percentage of powder particles with increasing scouring times was 52.173,51.474,and 51.755,and the percentage of average sand particles with increasing scouring fields was 46.905,47.701,47.541.The results showed that the content of clay particles and powder particles decreased with the increase of scouring field,while the content of sand particles increased with the increase of erosion field,indicating that the content of clay powder gradually decreased in the later stage of erosion,and the runoff was mainly eroded sand particles.(4)Under the test conditions,during the first test,the enrichment rate of clay particles and silt particles in the eroded sediment particles on the slope showed an overall trend of greater than 1,and subsequently decreased as the number of events increased.The enrichment rate of sand particles was less than 1 in the first session,and subsequently increased with the increase of scouring sessions.The above results indicate that with increasing erosion times,the content of eroded sediment particles on slopes is mainly composed of sand particles.The agglomeration rate of clay particles and powder particles in the eroded sediment on the slope is less than 1,and the agglomeration rate of sand particles is maintained at about 2.It shows that part of clay particles and powder particles were transported in the form of agglomerates,while sand particles are mostly transported in the form of single particles,and the agglomeration rate of clay particles,powder particles and sand particles gradually decreases with the increase of scouring times.