| Debris flow is a kind of typical geo logical disaster in mountain area,and it has tremendous destructiveness. Because of its complicated forming processed, debris flow has the characters of sudden eruption, rapid flow, high moment inertia and strong rectilinearity. As a result, when the debris flow goes through the bend, the fluid of bend channel will be thickened and the powerful scouring effect, which will lead to the obvious superelevation and huge damage on a bend. When the superelevation of band bank is high enough, the forceful scouring and deposition effect will be caused on the protective structures on the bend or buildings near the bend (such as highway,railway, residential construction etc.). Therefore, the study of the superelevation rule and the maximum superelevation position of debris flow curve has an nonnegligible significance to protect people’s life and property safety.Many researches on superelevation of the debris flow in bend, debris flow velocity and studies of bend radius have been conducted previously, however, there exists less studies on the nature of debris flow and the position of superelevation of debris flow.In this paper, several important factors influencing the superelevation of debris flow im bend will be analyzed and simplified by influencing factors, such as debris flow velocity, bend radius, the nature of debris flow(yield stress and density), the control variate method will be applied to study the effect caused by different factors on superelevation of the debris flow in bend and the position of superelevation of debris flow. Through a series of experimental study, establishing model and field verification, major conclusions will be obtained as follows:(1) Based on the analysis of the several groups of clear water velocity and curvature radius experimental data, the formula of superelevation in bend of clear water is obtained as: h =(BV2)/(Rg) which coincides with previous theoretical derivation,the reliability of the experimental method is illustrated.(2) Through the analysis of influencing factors and the previous study, the factors of influencing the superelevation of debris flow in bend are confirmed, they are debris flow velocity, bend radius, the debris flow property will have a great effect for bend superelevation, the yield stress has greatest effect, the density and bend width also have certain effects, the dimensionless stress (calculated by the yield stress, bend width, density and gravitational acceleration) is proportional to the bend superelevation, and through many experiments, The relationship between the coefficient of the superelevation calculation formula of debris flow curve and the yield stress of debris flow has been obtained as K=4.3×(τ/(ρgB))0.2 and the curve superelevation formula of debris flow has been obtained:h=K(BV2)/(Rg)=4.3×(τ/(ρgB))0.2 proving good applicability by field data.(3) Through the experiment of several groups of clear water velocity and curvature radius, the formula of the position of maximum superelevation of clear water in bend is concluded as: θ=90×V2/Rg.which coincides with previous experimental data, the reliability of the experimental method is illustrated.(4) Through the analysis of influencing factors, the factors of influencing the position of maximum superelevation of debris flow in bend are confirmed, they are debris flow velocity, bend radius, the debris flow property will have a great effect for the position of maximum superelevation, the yield stress has greatest effect, the density and bend width also have certain effects, the dimensionless stress (calculated by the yield stress, bend width, density) is proportional to the bend superelevation. Through the experiments of several kinds of debris flow with different flow velocity, different curvature radius and different yield stress, the formula of the position of maximum superelevation of debris flow in bend is obtained as:θ=20+AV2/Rg=20+56×V2/Rge80τ/(ρgB),proving good applicability by field data.The studies of rules among bend superelevation of debris flow, position of maximum superelevation, debris flow velocity, bend radius, the nature of debris flow(yield stress and density) in this paper provide a reference for engineering projects,location of highway railway, construction of guide groove in real life, which is to reduce or avoid the loss caused by debris flow disasters. |
