| Debris flow is one of the typical geological hazards in mountainous areas, and it has great dangers. Debris flow will release a large amount of accumulated material and huge energy In the impact moment,which has a great impact damage. The destructive power is mainly buried and impact damage, especially the impact is the most of significant. It can be known from previous studies that the impact force of debris flow is composed of two parts: the dynamic pressure and large stone striking force, and the main factors causing the destruction of the structure are the impact of the massive stone. Therefore, System and in-depth study on debris flow stone impact force calculation model, and thereby develop effective disaster prevention, mitigation measures, not only has great theoretical significance and great economic value, at the same time, to protect the people's safety of life has significance can not be ignored.The impact force of debris flow is not only related to the physical characteristics of the stone itself, but also related to the nature of the debris flow, Boulders impact force of debris flow is not only related to the physical characteristics of the stone itself,but also related to the nature of the debris flow. Because of the influence factors, it is difficult to study the impact force of debris flow. In this paper, the study of debris flow impact force of boulders into rolling stone in the air and mud two media impact study, assuming no matter what kind of medium, the rolling stones and the crashed object moment of impact and rockfall impact force calculation formula and quality,the relationship between elastic modulus and velocity is constant. Eventually debris flow impact force of boulders formula is more rockfall impact force calculation formula is just the coefficient changes. The coefficient of the calculation formula of the impact force of debris flow is related to the grade of debris flow, yield stress, bulk density and so on.By dimensional analysis derived rockfall impact force influence factors of impact object quality, impact velocity, impact object and the crashed object of elastic modulus and impact angle direction and plane and get the relationship between the influencing factors. Then through the experimental design, data collection and analysis to verify the theoretical derivation, finally obtained the rockfall impact forcecalculation model, In order to make the rockfall impact force calculation model is applied to the practical engineering, Finally, the calculation formula of the impact force of debris flow is obtained through the analysis of several groups of experiments.In this series of experiments to get the conclusion that there are a few points.(1) In this paper, a rolling stone dimension harmony impact formula by dimensional analysis method. The formula is F=C(EM2V4)1/3f(sina), From the formula can see rockfall impact force and impact object of mass m, impact velocity V, e complex elastic model and impact angle in the plane of the direction and a sinusoidal related. among them, E=E1E2/(E1+KE2E1),E1 is the modulus of elasticity of striking object, E2 is the modulus of elasticity knocked objects.(2) Through multi group experiments and data analysis, the final determination of the coefficient is C=0.261,K=2,f(sina)= sin1/2a?Therefore, the formula for the calculation of the impact of the rolling stones is F=0.261(E1*E2/(E1+2E2)V4M2)1/3sin1/2a?The model is in good agreement with the experimental data and field data at home and abroad, and the model is not limited by large scale,so it can be used in field practice.(3) On the basis of experiment of rockfall impact force, after the experimental group obtained in water medium, rockfall impact force calculation model of speed, quality, and comprehensive elastic modulus relationship has not changed. Just a change in the coefficient, finaly, C=0.212,The calculation formula of rockfall impact force under water for F=0.212(E1*E2/(E1+2E2)V4M2)1/3sin1/2a.(4) The experiment was carried out to replace the pure water medium into a pure slurry medium. The magnitude of the coefficient C in the impact force calculation model decreases with the increase of t/rgh and get a dimension of harmonious relationship C=0.19(t/rgd1)^(-0.1), Where t is the debris flow yield stress, r is the density debris flow, d1 is the particle size of the slurry,d1=0.0005 m, In the slurry medium, rockfall impact force calculation formula of C coefficient is less than the coefficient of water. From the point of view of energy, the material in the mud can absorb the impact energy more than the clear water, therefore, it is less than the impact force in the clear water.(5) With 1mm-2mm, 2mm-5mm, 5mm-10 mm, 10-20 mm, 20mm-50 mm these five kinds of particle size of different yield stress and bulk density of the debris flow so that five kinds of particle size can be suspended in the slurry, Then carries on the experiment, The coefficients of the model for calculating the impact force of the debris flow in the debris flow are obtained by the multi group experiments. C=0.225(?/rgd1)(-0.1)(d/d0)0.05,Where d is the diameter of the test suspension, and d0 is the slurry of sand particle size, d0 is a constant,d0==0.002 m. When the d/d0 rapid increase, the C/(t/rg)(-0.1) increase is not obvious. This also shows that under the debris flow medium, rockfall impact force calculation formula of the coefficient is relatively stable, not with the suspended particle diameter increasing too obvious.(6) Through the collation of data, the calculation model of impact force of debris flow is finally obtained. F=0.225(?/rgd1)(-0.1)(d/d0)0.05(EM2V4)1/3sina0.5 And the model is in good agreement with the experimental data and the field data at home and abroad. |
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