Experimental Study On Infiltration And Self-Filtration Process Of Packing Particle

Soil in the form of packing particle matter are widely distributed in nature,and geological disasters such as landslides are often caused by deformation of infiltrating packing particle matter.Differentiated physical and mechanical properties determine the difference in seepage deformation.The self-filtration process of migration and deposition of fine particles in the accumulation of particulate matter under hydraulic action will cause erosion and blockage of internal channels,causing pore water pressure rising and regional quality loss or accumulate.When the phenomenon of fine particle movement transforms from accidental individual movement to group behavior under the critical threshold condition,and presents a certain law in spatial distribution,it can affect the overall macroscopic seepage law.The internal selffiltration process of part of the packing particle matter under the action of osmosis can cause the fine particles inside the medium to easily migrate,and then cause internal erosion or clogging,leading to parameter distribution variation,and even become one of the influencing factors for landslides in this type of packing particle matter slope.In order to understand the evolution process of the self-filtration process and the law of mass erosion and seepage channel deposition and blockage in the accumulation of particulate matter,the evaluation of internal stability factors and the characteristics of self-filtration in slopes are provided from the perspective of meso-particle movement and macro-seepage development.In this paper,the physical model test and theoretical analysis are combined to study the self-filtration process of cylindrical specimens in infiltration under different media conditions and external hydraulic gradients.Combining the infiltration effect of multi-factor cylindrical specimens to explore the dominant channel in the slope Influence on the selffiltration process.The main work content and results are as follows:(1)Under the gradual development of hydraulic gradient,the cumulative mass erosion rate development and the nonlinear development characteristics of seepage of accumulation particle unit affected by multiple factors.Using transparent fused silica sand as test material,a multifactor response surface test was designed for cylindrical infiltration test.The micro-particle movement and macro-seepage development were analyzed by microscopic image and seepage development data,and the multi-factor erosion rate response surface model was obtained.The influence of various factors on the erosion rate is as follows:hydraulic gradient,gradation unevenness,porosity,and the combination of the largest cumulative erosion rate is(Cu=20.47;n=0.40).It is observed that the flow velocity develops into a nonlinear process with the hydraulic gradient decreasing first and then increasing.(2)Under constant hydraulic gradient,the logarithmic growth law of cumulative erosion rate of accumulated particles in internal unstable state with time,and the time-history characteristics of flow velocity differentiation development with critical gradient as the boundary.The causes of seepage mutation point caused by internal hydraulic shear failure are analyzed,and the influence of critical hydraulic gradient on the infiltration of accumulated particles is analyzed.Different constant hydraulic gradient infiltration tests were conducted on the samples with obvious hydraulic erosion effect and active internal particle movement.The results show that the erosion rate of the sample develops into a time-dependent progressive process.When the erosion hydraulic gradient is lower than the critical gradient,the erosion develops slowly and the fluctuation is low.When the erosion hydraulic gradient is of high critical gradient,the erosion develops rapidly,and the seepage development gradually changes from fluctuation to gentleness.According to the test data and the Sterpi data model,the timehistory development piecewise function of cumulative mass erosion rate with the critical hydraulic gradient as the boundary is calculated.(3)The internal stability criterion of quartz sand accumulation granular material considering the gradation uneven coefficient and porosity.The typical judgment criteria of Istonima criterion,Kezdi criterion,Burenkova method,Wan&Well method and Andrianatrehina method were used to calculate and compare the d60/d10,(d15/d85f)max?d90/d60?d90/d15 of the test material and the upper and lower levels of the specimen cylinder.The analysis and judgment results show that the Istonima criterion is relatively accurate.Aiming at the problem of incomplete consideration of main control factor+strong auxiliary factor of particle accumulation body instability under multi-factor simultaneous action,a judgment criterion considering the influence of gradation parameters and porosity is proposed.(4)The positive feedback characteristics of mutual promotion between dominant channel development and internal self-filtration process in slope infiltration.The small-scale idealized slope infiltration self-filtration model test was carried out.According to the guiding ideology of“abstract purification",the pre-set porosity parameters were achieved by adding soluble particles for sample preparation to accelerate the characterization of the internal pore channels and the development of dissolved cavities in the accumulation particles.The test process shows that the accelerated characterization method of soluble particles is feasible.The development of dominant seepage channel has an important influence on the positive feedback process of hydraulic erosion and fine particle migration,which promotes erosion-accelerated flow velocity in the channel-accelerated erosion.In this paper,a series of experiments were carried out to study the self-filtration process in the infiltration of accumulated particles.Transparent fused silica sand particles are used to replace opaque natural materials.Simple laboratory tests are used to weaken the prediction of non-critical factors.The target parameters(particle size distribution,porosity and hydraulic gradient)are combined and the combination of sensitive factors is studied.The sensitivity factors and erosion-clogging characteristics of self-filtration process of accumulation particles under multi-factors were explored to understand the evolution process of internal self-filtration process.From the perspective of microscopic particle movement and macroscopic seepage development,it provides a theoretical basis for judging the influencing factors of infiltration self-filtration of accumulation particles and the utilization and treatment of erosion-clogging phenomenon in self-filtration process.