| In the thaw period of spring,repeated freezing and thawing damages the stability of the soil and reduces the corrosion resistance of the soil.In order to determine the temporal and spatial distribution characteristics of erosion and sediment production on the freeze-thaw slope and the main influence factors of the sediment concentration on the freeze-thaw slope,the scouring effect was determined.This article passes 2(10°,15°)slopes,4(4.5L/min,6.5L/min,8.5L/min,10.5L/min)flow rates and 4(2cm,5cm,10 cm,15cm)The initial thawing depth combination was subjected to the field outer diameter flow erosion test.Observational flow width,flow velocity,runoff depth,access to sand samples,observation of drowning volume.The rare earth element(REE)tracer technique was used to determine the concentration of rare earth elements in the sand samples and the amount of sediment produced in each trace area was calculated.The spatial and temporal distribution of sediment production on the frozen-thawed slope was analyzed.The grey correlation method and stepwise regression method are used to analyze the main influencing factors of sediment concentration and its response relationship.The main results obtained are as follows:(1)The characteristics of spatio-temporal changes of sediment yield on freeze-thaw slopesUnder the same initial thawing depth,the soil erosion and sediment yield increased with the increase of slope and discharge,and the erosion occurred at the first slope of the slope,accounting for 68.24% of the total sediment yield,and the sediment yield at the 3rd slope was always When the slope is the same,the amount of sediment produced by erosion increases with the increase of initial thawing depth and flow rate;the amount of sediment produced by freezing and thawing slope decreases along the direction of slope and along the direction of soil depth;La element The sediment yield in the tracer area increased first and then decreased with time.The trend of sediment yield with erosion time in other trace element areas was basically consistent with the variation trend of sediment yield in the La element tracer area.(2)The characteristics of sediment concentration on freeze-thaw slopesDuring the scouring of freeze-thaw slopes,the trend of the sediment concentration along the slope of each slope segment increases with time and then decreases towards the end.The sediment concentration of the first slope segment accounts for the total sediment concentration in the stream.From 68% to 72% of the total,the sediment content of the second slope segment accounts for 74%~89% of the total sediment concentration,and the sediment content of the first slope segment accounts for 94%~100% of the total sediment concentration.(3)The main influence factors of sediment concentration on freeze-thaw slopesThe grey relational analysis shows that the order of the correlations between the influencing factors of the first slope and sediment concentration is: flow rate> slope> unit flow power> Froude number;the correlation degree between the impact factors of the second slope and sediment concentration The order of size is: flow rate> slope> unit flow power> Froude number;the order of correlation of each influencing factor and sediment concentration in the third slope is: flow rate> Froude number> slope> unit flow power;slope surface The order of correlation of each impact factor and sediment concentration is: flow rate> slope> Froude number> unit flow power.(4)Obtained a prediction model for sediment concentration on freeze-thaw slopesThere is a linear relationship between the sediment concentration and the influencing factors on the surface of freeze-thaw slopes.The calculation equation for sediment concentration based on flow velocity,flow rate,unit flow power and Froude number is established in the first slope section(R2=0.96);The calculation equation for sediment content of the flow based on the flow velocity,flow rate,Froude number,and unit flow power was established on the slope section(R2=0.89);the sediment concentration of the flow based on Froude number and unit flow power was established on the third slope section.The equation is calculated(R2=0.768).The calculation equation for sediment concentration based on flow,initial thawing depth,Froude number,and unit flow power is established for the entire slope(R2=0.914). |
PDF Full Text Request