Studies On The Filtering Mechanism Of Foam Plastics

The filter layer is an important seepage control measure in water conservancy and hydropower projects,and also an important part of the infiltration system in the construction of sponge city.The traditional sand and gravel filter layer is easy to be clogged and it is difficult to replace after clogging,resulting in a decrease in the effect of the filter layer.Foam plastic filter is a kind of polyurethane polymer material.As a new type of filter material,it is easy to replace after clogging,and has low density,strong impact resistance and strong environmental adaptability.It has been applied in engineering practice and has achieved good results.However,the research on foam plastic filter is still lack of microscopic mechanism.In this paper,the microscopic pore characteristics of foam plastic filter,the variation of the permeability coefficient of foam filter material with time and the distribution characteristics of the silt plugging particles in the pore system are studied by means of SEM and silt plugging test.The main contents and conclusions of this paper are as follows:(1)The pore image of the foam plastic filter material is obtained by scanning electron microscope.After numerical treatment,the pore geometry parameters are measured and the evaluation parameters of the pore geometry characteristics are calculated.The results show that the correlation of the diameter of the equal area circle,the diameter of the equal circumference,the maximum Fleet diameter and the porosity is obvious,and the pore structure is approximately round.Shape,malformed structure is less.(2)The clogging test was carried out under the condition of the same concentration and two kinds of suspended particles.The results showed that the permeability coefficient decreased rapidly with time,and the descending speed slowed down,and finally tended to be stable.The permeability coefficient of the clear water and the permeability coefficient after the clogging are both negatively correlated with the sample density.(3)The samples were cured by high permeability epoxy,and the image of the clogging material was obtained by scanning electron microscope.After numerical treatment,the geometric size and position distribution of the clogging particles were analyzed.The results showed that the clogging rate decreased from the upstream to the downstream,and was negatively correlated with the sample density,and the particle geometry scale was negative.The seepage path of the particle size decreases from upstream to downstream and negatively correlated with porosity.