Permeability isBiomembraneThe characteristic refers to the ability of water net movement caused by concentration difference, such assoilAnd porousrockMeans that it allowswaterAbility to pass;aboutAir diffuserFor, it means to allowatmosphereAbility to pass.Broadly speaking, in addition to water, under the influence of external environment, such as:earthquake、nature(Sun, wind, snow, lightning, etc.) can also make the material permeable.Permeability caused by the same soluteosmotic pressureSize and solute molecule orIonsThe number of is proportional.
Chinese name
Permeability
Foreign name
permeability
Nature
Characteristics of biofilm
Definition
Capacity of net movement of water caused by concentration difference
influence factor
Osmotic pressure, number of solute molecules or ions
Permeability refers to the ability of a material to allow fluid to pass through without damaging the medium structure.For example, soil and porous rock refer to their ability to allow water to pass through.aboutAir diffuserFor, it refers to the ability to allow air to pass through.In a broad sense, besides water, materials can also be permeable under the influence of external environment, such as earthquake, nature (sun, wind, snow, lightning, etc.).
Permeability coefficient
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Permeability coefficient is also called hydraulic conductivity.stayIsotropic mediumIn, it is defined as the unit flow rate under the unit hydraulic gradient, which represents the difficulty of fluid passing through the pore framework, and the expression is: κ=k ρ g/η, where k is the permeability of porous media, which is only related to the nature of the solid framework, and κ is the permeability coefficient;η is the dynamic viscosity coefficient;ρ is the fluid density;G isGravitational acceleration。stayAnisotropic mediumThe permeability coefficient is expressed in tensor form.The greater the permeability coefficient,rock permeability The stronger.Permeability coefficient of strongly permeable coarse sand gravel layer>10m/day and night;The permeability coefficient of weakly permeable sandy soil is 1~0.01 m/day and night;The permeability coefficient of impervious clay is less than 0.001 m/day and night.It can be seen that the soil permeability coefficient depends on the soil texture.
Soil permeability
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There are many factors affecting the permeability of soil, such as soil type, densityStress state, water flow pattern andHydraulic gradientEtc.[1]
Soil permeability also plays an important role in the migration of pollutants.The permeability of the soil reflects the tightness of the soil. The tighter the soil is, the worse its permeability is. The slower the water movement is, the worse the migration ability of pollutants is. On the contrary, the looser the soil is, the better its permeability is. The faster the water movement is, the faster the migration ability of pollutants is.Therefore, the permeability of soil also directly affects the migration capacity of pollutants.[2]
The empirical infiltration coefficient K is an important indicator reflecting the soil infiltration capacity. It represents the average infiltration rate per unit area in the first unit time (1min) after the beginning of soil infiltration or the cumulative infiltration amount per unit area at the end of the first unit period. The value depends mainly on the soil structure and condition at the time of infiltration.[3]
The empirical infiltration index a is an important indicator reflecting the attenuation of soil infiltration capacity. The larger the value, the faster the attenuation of infiltration, and the smaller the value, the slower the attenuation of infiltration.The value mainly depends on the change of soil structure caused by soil wetting.[3]
