Research On Clay Minerals And Yield Stress Of Debris Flow By Experiments

China is one of the countries in the world with debris flow were most widespread,the largest number of the most affected and serious debris flow disaster. It is widely distributed in China's 12 provinces and autonomous regions of western region, such as, Sichuan, Tibet, Yunnan, Guizhou, and Gansu. According to statistics, It has identified more than 15,500 articles, threatening over a hundred cities and towns. Debris Flow disaster serious constraining construction and economic development in mountain areas.It is a very difficult task of disaster prevention. So the researches of debris flow control theory and control techniques are the present difficult and hot spot.One of the major hazards of debris flow is deposit buildings and engineering facilities. September 24,2008, West hillside gully, it is a debris flow gully nearing old Beichuan county, happened a large of debris flow after Wenchuan earthquake. The deposition of debris flow reached 12m; August 13,2010, Wenjia gully, it is a debris flow gully, happened in Mianzhu Qingping, Sichuan province. The largest deposition in Mianyuan River is far more than 15m, damaging 479 houses. Qingping Township hospitals, schools and other facilities were severely buried, more than 300 acres of farmland were destroyed, the direct economic losses of RMB 430 million. Deposition is the main form of debris flow disaster. The deposition thickness of debris flows is the most important parameter both of debris flows and of the evaluating and preventing the hazards of debris flows.Based on previous research and pre-accumulation, First, we obtained the density of debris flow, the maximum sediment thickness, slope gradient sedimentation through field investigation to calculated yield stress of debris flows; Then, research the relationship of the yield stress and concentration of solid particles and composition and content of clay by adopt deposition experiments in order to obtain calculation method of the yield stress of debris flow. Finally, according to collected deposition thickness of the field, density, slope of debris flow, and analysis clay minerals composition and percentage of content of debris flow, verify and amend the calculation of debris flow yield stress. Ultimately achieve a more comprehensive understanding of debris flow characteristics of the yield stress. Serving the debris flow disaster prevention and mitigation engineering.By comparing with the results of the laboratory experiment and the data in the field, We have achieved the following results:(1)The clay mineral is one of the product of rock efflorescent, the characteristic of clay mineral related with the characteristic of rock. The most common clay minerals:kaolinite, chlorite, illite and montmorillonite. Their water resistance, swelling, hydrophobicity and adsorption in the debris flow not only influence with for debris flow to move, but also affect the debris flow to erosion and deposition. Debris flow concentration of solid particles will cause movement of debris flow is very complex; this change has great influence on rheological properties of debris flow. Preparation of the different debris flow experiment bulk density, particle size and composition and content of clay. Considered the yield stress of debris flow, Volume concentration of solid particles and composition and content of Clay mineral are two important parameters for the yield stress. (2) Composition and content of Clay mineral and yield stress of debris flow has a very close relationship. The same clay content and the same volume concentration of solid In order to study the relationship between clay min. and yield stress of debris flow:montmorillonite> illite> chlorite> kaolinite.(3) The relationship between Volume concentration of solid particles and debris flow yield stress is positive exponentially:τ=0.3351e11.756CV The relationship between content of clay and yield stress of debris flow is positive exponentially. But,when Compared with the Cv≤0.55, the index had a sudden change. Cv≤0.55,τ=4.8976e0.1126P, Cv> 0.55,τ=23.32e0.1126P By comparing the two factors(concentration of solid particles and clay mineral), the relationship between clay minerals and yield stress is stronger than the relationship between volume of solid concentration and yield stress. (4)Considering the relationship between clay minerals and yield stress and the relationship between volume of solid concentration, Different clay minerals have different physical properties, Given different clay minerals a different coefficients, the formula,with concentration of solid particles and composition and content of clay,were established on:T=30 SC 2e22 CP T-debris flow yield stress (pa); S-coefficient associated with the clay; C-the volume concentration of debris flow; P-content of clay (%).(5)Through a volume concentration of debris flow(Cv=0.453), We discussed the relationship between the mixed clay minerals and yield stress:When the clay content of less than or equals 20%(the Scope has covered the range of clay content in debris flow, the clay content is generally 4%-10% in debris flow.), the yield stress of mixed clay minerals is approximately equal to superposition of values of the yield stress of a single clay minerals. (6) The difference between the nature of the debris flow through density of debris to determine the strength of viscous debris flow is unreasonable, should consider the content of clay.(7) By comparing with the results of the laboratory experiment and the data in the field, Although some deviations of field data and laboratory test data, have a certain universality of this formula after the amend density, content of clay mineral, the result is supply of scientific parameter for prevention and control of debris flows.This paper added to the clay minerals into the yield stress of debris flow, Although fill some gaps in the current study, More restrictions factor, such as lack of test platforms and deviation of measurement data, this paper still many shortcomings:(1) In this study, the largest solid particle in the composition of debris flow is 10mm, Although the particle size close to the actual debris flow compared with the previous slurry, But it cannot match the actual particle size; (2)Measurement of content of clay is not accurate。at present, XRD and SEM tests were done only qualitative-quantitative analysis, the XRD test system deviation is about±10%; (3) In the experiment, using clay minerals only represent the local characteristics of clay minerals, Thus, the clay minerals of different regions will affect the accuracy of calculation of the yield stress; (4) there are some deviation between the experimental studies and field measurements, Mainly in the particle size, clay content, slope, etc. How to contact the experimental results and field data require further study.