Study On Permeability Characteristics And Fine Particle Migration Law Of Deposited Soil In Debris Flow Channel

Debris flow is a kind of special fluid between landslides and floods and is common in mountainous areas.Its sudden outbreaks are fierce and extremely damaging to people's personal and property safety.In recent years,the ecological environment has been partially improved,but the governance capacity is nowhere near the speed of destruction.Though the frequency of geological disasters in Sichuan has declined,the economic losses and casualties caused by each disaster are still on the rise.Reducing the severity of debris flow disasters and improving the efficiency of debris flow prevention and cure have become urgent issues.The permeability characteristics of the channel deposits and the movement law of fine particle during permeability process are not only the key factors affecting the scale and the severity of a debris flow disaster,but also provide basic information for the prevention and cure of debris flow.Therefore,based on laboratory experiments and considering influences such as percolation time,fine particle content,and discontinuities of grain-size distribution within a certain thickness in anti-granular order stacking,this paper studies the permeability characteristics of the loose deposits in the debris flow channel under the inflow of water and analyzes the fine particle migration law during permeability process.The main conclusions are as follows:?1?The permeability coefficient of the debris flow deposited soil changes with the percolation time,and the change law is affected by the particle composition of the soil.The trend of the permeability coefficient changing with time is related to the fine particle content,while the discontinuity of the particle gradation affects the sensitivity of how the permeability coefficient changing with time factors.?2?Fine particles are still the key factor affecting the permeability coefficient in the gap-graded deposited soil which is within a certain thickness range of the debris flow channel.There is a significant negative exponential function between them.Moreover,how the permeability coefficient and the fine particle content are related is affected by the discontinuity of particle size distribution-the more discontinuous the grain gradation of the stacked soil is,the more obvious the permeability coefficient is affected by the fine particle content.s?3?There is a better power function relation between the permeability coefficient and the kurtosis coefficient of soil.The more discontinuous the vertical particle gradation is,the greater the permeability coefficient would be.If the missing range of intermediate particle size is taken as a single variable,the permeability coefficient and kurtosis coefficient show a significant linear relationship when other conditions remain unchanged.?4?When the soil is percolated,the fine particles migrate to the direction of water flow.After percolation,the fine particles in the upper part of the soil decrease,while fine particles in the lower part either migrate or accumulate,and the content of fine particles is complicated.The migration law of fine particles is related to the discontinuity of particle gradation.The more discontinuous the particle gradation is,the more obvious the migration and accumulation of fine particles in the process of permeability would be,and the more likely it is to cause the rapid change of pore water pressure and lead to the instability and liquefaction of soil.?5?Consider the influencing factors of soil seepage performance,such as fluid viscosity coefficient?,porosity n,fine particle content P₂,kurtosis coefficient B_*,based on dimensional analysis,a calculation model for the discontinuous grading particle permeability coefficient ???was established.