Study On Erosion Characteristics And Erosion Rate Model Of Fine Particle Soil And Mixed Soil

Erosion of soils is an essential cause of erosion damage in water-related structures such as bridge foundations and rock dams.The erosion are usually characterized by the critical shear stress and other erosion parameters.It is essential to clarify the relationship between soil properties and erosion parameters.However,the basic physical properties of geotechnical bodies are coupled with each other,and the relationship between scour parameters and soil properties needs to be further clarified.The physical characteristics of mixed soil bodies are more complex than those of simple soil bodies.There is still a lack of data on erosion function apparatus in the soil mixture.There are differences in the prediction performance of erosion rate models for different soils,and the index setting of shear stress in the existing erosion models is not reasonable.In this thesis,the erosion database of fine-grained soils was collected,experimental data containing 98 sets of erosion apparatus function tests and physical and mechanical properties of soils;three principal component variables were obtained by principal component analysis of seven conventional soil physical parameters,which solved the mutual coupling problem between soil parameters of fine-grained soils.The three principal component variables were coupled with the dimensionless over-shear stress model of fine-grained soils.A nonlinear regression prediction model is proposed by multiple regression analysis,which can predict the erosion parameters by soil physical parameters and obtain the erosion rate characteristics of the soil body quickly;the data set is simulated by the least squares support vector machine method,and good results are obtained.Erosion function apparatus tests were conducted on gravel-clay soil mixtures,and erosion rate curves were obtained for uniform gravel-clay soil mixtures and non-uniform gravel-clay soil mixtures;in the mixed soil,the increase of coarse particle diameter or median particle diameter enhances the erosion resistance of the soil for the same clay content.The starting shear stress of the mixed soil is proportional to the diameter of coarse particles.By analyzing the relationship between soil physical parameters of mixed soil and Wilson erosion model parameters,it is proposed that the erosion parameters b₀ and b₁ of soil mixture are by the power function relationship with the dry density and water content of mixed soil,respectively.The erosion parameters b₀ and b₁ also have a similar power function relationship.A single erosion parameter can characterize the two types of mixed soil characteristics in the test.By analyzing the exponential relationship between erosion rate and shear stress,the erosion curve characteristics of different soils are given:the increase of coarse grain size of sand-clay mixed soil and the increase of cohesive force of clay are associated with the nonlinear erosion behavior of the soil;the nonlinear erosion behavior is weakened by the increase of clay grain content of sand-clay mixed soil;it is proposed that in different soil It is proposed that a single exponent of shear stress as a constant under different soil conditions is not reasonable.A new inductive equation is given by redefining the exchange time parameter in Wilson’s model through dimensional analysis and combining the results of the exponential analysis.A modified erosion rate model is proposed based on Wilson’s model.After verification and comparison,its prediction effect is better than the original model.The prediction accuracy under low-stress conditions is significantly improved.