| The soil erosion in the Pisha sandstone area has been called ’Earth Ecological Cancer9 by experts.The erosion problem caused by Pisha sandstone in the hilly area of Ordos is particularly prominent.The local rainstorms are concentrated and strong,which causes the erosion type of the area to be dominated by water erosion and accompanying gravity erosion.Rainfall and runoff are the two main forces for erosion and sediment production in the Ordos Pisha sandstone area.Thus,a thorough understanding of the relationship between the erosion of Pisha sandstone and the characteristics of flow hydraulics rainfall induced is the basis for studying the hydraulic erosion mechanism of red Pisha sandstone in Ordos.Through the artificial rainfall simulation,we carried out rainfall erosion test under different rain intensities and different slopes firstly,and established the relationship between rain intensity,slope,hydrodynamic parameters and the erosion amount of the saturated both weathered Pisha sandstone slope.Secondly,the rainfall erosion test under different rain intensity and different density was carried out,and the direct shearing instrument was used to directly measure the cohesive force and internal friction angle of the weathered Pisha sandstone slope,which reveal the infiltration,runoff and erosion characteristics of different density slopes.The results suggest:1、To the saturated both weathered Pisha sandstone slope,the flow rate on th e slope doesn’t change obviously when rainfall intensity is between Omm/h and 80 mm/h,however,it increases rapidly when rainfall intensity is higher than 85mm/h.R eynolds number and stream power increase with rainfall intensity.Flow share stress shows a trend of increasing first and then decreasing slightly,its maximum value occurs when rainfall intensity is around 90mm/h.Sediment transport rate has a exp onental growth as either rainfall intensity or gradient increases.2、The correlation degree between each hydrodynamic parameter and sediment transport rate under grey correlation analysis is between 0.685?0.733.The highest value is the stream power.Using the hydrodynamic parameter as a variable,the prediction model formula was programmed according to the Akaike information criterion.Grey relational analysis and the Akaike information criterion all indicate that stream power of the water flow is an important parameter that affects the erosion and sediment yield of the rsaturated both weathered Pisha sandstone slope in Ordos.3、The incipient velocity under each slope of the test conditions increases with the increase of rain intensity,that is,the compaction effect of raindrops on the slope is obvious.Through the force analysis,the formula of the incipient velocity of the saturated both weathered Pisha sandstone slope is established.The calculated values of the verified formula are consistent with the measured values.4、To the slopes with the density of 1.5g/cm3、1.6g/cm3 and 1.7g/cm3,the erosiln amount has the highest sensitivity with infiltration rate,cumulative infiltration depth and flow respectively through the analysis of slope erosion of different densities.Both sensitive analysis and direct shear test indicate that flow is the main cause of the erosion of 1.7g/cm3 weathered Pisha sandstone slope. |
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