| The Pisha sandstone area in the Ordos Plateau is a typical ecologically fragile area with high erosion modulus and strong sediment concentration in the Yellow River Basin.The dynamic erosion of water,wind and freeze-thawing alternates and forms a complex composite erosion system.Due to the weak anti erodibility of Pisha Sandstone,it leads to a high-intensity erosion and sediment production process in the erosion environment of composite power,which transports a large amount of coarse sediment for the Yellow River and poses a threat to the production,livelihood and social development of the middle and lower reaches of the Yellow River.Therefore,taking Erlaohu Gully watershed in the Ordos Plateau as the research area,the complex erosion experiments with different dynamic combinations were carried out through indoor simulation to study the response relationship between the complex erosion process and the sediment transport process,and reveal the sediment transport mechanism on the Pisha sandstone slope under the action of compound erosion.The results show that:(1)The change of runoff and sediment yield process of Pisha Sandstone slope under composite erosion was discussed.The duration of runoff generation under composite erosion is 2 to 3 times longer than that under single water erosion,and the effective erosion time is extended by 10%-13%.The composite erosion process makes the runoff increase gradually,and the growth rate reaches 21%,the sediment yield increases up to 183%.(2)The characteristics of water-sediment relationship of arsenic sandstone under compound erosion are analyzed.The coefficient of determination of the power function between the cumulative runoff and the cumulative sediment transport in the erosion process with different dynamic combinations is R~2 > 0.98.Under the action of compound erosion,with the increase of the types of erosion forces,the water-sediment relationship shows a better synchronous trend.(3)The distribution characteristics of erosional sediment particles in Pisha sandstone are described.The MWD of erosion sediment particles is as follows:freezing-thawing wind and water erosion(0.76mm)> freezing-thawing and water erosion(0.75mm)> single water erosion particle(0.68mm);With the increase of the types of erosion dynamics,the variation of the particle size becomes more intense during the erosion process.Under freezing-thawing and water erosion and freezing-thawing wind and water erosion,only the enrichment rate of sand content is greater than 1,and the highest is 1.40 and 1.71,respectively,indicating that the combined erosion can significantly affect the grain distribution of erosional sediment,resulting in the enrichment of a large number of coarse particles.(4)The variation characteristics of the particle composition of the eroded sediment in Pisha Sandstone are analyzed.The results show that there is a clear change trend of each particle size under the composite erosion.The composition action of erosion dynamics can change the content proportion of each particle size in the eroded sediment,make a large number of coarse particles output and fluctuate violently in the process of erosion.Under the action of freezing-thawing,water erosion,the clay content of eroded sediment decreased by 43%,and the sand content increased by 22% at a relatively rapid rate;under the action of freezing-thawing,wind erosion and water erosion,the clay content decreased by 47%,and the sand content increased by 27%.Freezing-thawing and wind erosion have obvious screening function for eroded sediment.(5)The response relationship between Pisha sandstone and sediment transport in the process of composite erosion is revealed.With the increase of the types of composite erosion dynamics,the rill development rate is faster and the erosion area is larger.Sediment yield increased significantly with the active rill development stage,and the coarse particles were enriched.In the erosion process,the loading mode tended to be the main sediment transport mechanism. |
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