| Pisha sandstone area is a typical ecological fragile area and a concentrated source area of coarse sediment in the Yellow River Basin.Under the influence of various erosion forces,soil erosion is very serious.The study on the process and law of composite erosion of Pisha sandstone under the action of wind,water,freeze-thaw and other forces provides a theoretical basis for the control methods and measures of Pisha sandstone area,which is of great significance for the ecological protection and soil erosion control of the area.Through the establishment of a multi dynamic erosion test model in the rainfall Hall of the Key Laboratory of soil and water loss process and control in the Loess Plateau of the Ministry of water resources,and the simulation of indoor wind,water and freeze-thaw tests under different slopes and different operating forces,the process of the production of Pisha sandstone under the condition of multi dynamic erosion combination is studied,and the changes of hydrodynamic parameters under different dynamic combinations are clarified Combined with field observation and test,the contribution rate of different erosion forces to the erosion of soft rock slope is revealed.The results show that:(1)Freezing and thawing can increase runoff and sediment yield by more than 20% and 40% respectively;wind erosion can increase sediment yield by 13% ~ 17%.Under the condition of low slope,the process of runoff and sediment yield of multi dynamic combination is more stable than that of high slope,and the increase of slope is easy to induce the occurrence of local collapse erosion.At the same time,with the increase of slope,the process of runoff and sediment yield is more obvious and the fluctuation range is larger.(2)Under the condition of different slope and erosion dynamic combination,the relationship between cumulative sediment yield and cumulative sediment yield is a good power function.When the runoff is the same,the sediment yield under different erosion conditions is from large to small in order of freeze-thaw wind hydraulic erosion,freeze-thaw hydraulic erosion and hydraulic erosion.The relationship between water and sediment is greatly affected by freezing and thawing,less affected by wind,and the slope has a great influence on the trend of the relationship between water and sediment.(3)In the process of rainfall,the velocity of runoff increases with the increase of erosion force.Under different slope and dynamic combination conditions,the flow on the slope is laminar flow.The flow pattern is mainly related to the type of runoff.The surface flow is mostly slow flow,while the gully flow is jet flow.The water content of the surface layer of the soft rock increases with the increase of the force at the beginning of the rainfall,and then decreases with the increase of the force.The initial infiltration rate increases with the increase of the erosion effect of the camp force,and the influence of the compound erosion on the slope infiltration decreases with the rainfall.(4)With the increase of the types of erosion forces,the topographic change of the slope will be accelerated,and the amount of erosion will increase with the increase of the erosion forces.The effect of freezing and thawing on the change of topography is greater than that of wind.The contribution rate of the erosion caused by stripping single erosion force,indoor simulated hydraulic erosion,wind erosion and freeze-thaw erosion is 23.8%,15.9%,60.3%,and the contribution rate of the three effects is freeze-thaw erosion > hydraulic erosion > wind erosion.The contribution rates of hydraulic erosion,wind erosion and freeze-thaw erosion are 58.5%,23.9% and 17.6% respectively. |
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