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Investigation On The Development And Properties Of New Anticlogging Filtration Material

Posted on:2003-09-29Degree:DoctorType:Dissertation
Country:ChinaCandidate:L F LiuFull Text:PDF
GTID:1101360095453851Subject:Textile materials and textile design
Abstract/Summary:PDF Full Text Request
Geosynthetics, which have excellent physical, chemical, and hydraulic properties, are very promising materials and widely used in various civil construction engineering, water conservancy project, airport, railway, highway, dock, and tunnel etc. Especially for needle-punched nonwoven geotextiles used as filtering material, they have very good filtration and drainage functions because of their unique three-dimensional fiber web structure. However, needle-punched nonwoven geotextiles are traditionally single layer structure made of one or two blended fibers. So clogging is often caused in powder clay engineering, that may greatly decrease the filtering properties of geotextiles, even deprive of their functions as filtering material. At the same time, geotextiles in our country have just begun to be researched and applied, thus the related products have little difference in structures and low technological value, which infinitely affect their popularization and application. According to this situation, the permeability and filtration performance of needle-punched nonwoven geotextiles are analyzed and discussed both theoretically and experimentally in detail, and a new kind of filtering material is designed and produced in this thesis.In theoretically study, a mathematical model of the relation between structure of nonwoven geotextiles and their permeability is established on the basis of Darcy's law and drag-force theory. The relation between structure of nonwoven geotextiles and their opening size distribution is analyzed according to Poisson Polyhedron theory, and a mathematical model of geotextile opening size distribution and the probability of soil particles passing or clogging in geotextiles is formulated. A single layer or muti-layered sample may be used in actual testing of the vertical permeability coefficient of geotextiles, so the relation between them is also theoretically analysed according to Darcy's law. Besides, the mathematical model about permeability and filtration performance of mutilayered geotextiles consisting of fiber layer with different finess is also derived.In application research, a new anticlogging filtration material is developed. It is a kind of needle-punched nonwoven geotextile lapped over by two fiber layers withdifferent finess, therein, one layer is made of finer fiber and has smaller pores so as to retain most soil particles; the other layer is made of coarser fiber and has higher strength. The new materials have obvious advantages in function and property, and are especially suitable for powder clay areas in South China which usually have very smaller particles. Furthermore, five anticlogging filtration material samples with different porosity are produced by changing needle-punching density in order to analyze the relation between geotextile structures and their permeability and filtration performance.In experimental study, the validity of the mathematical models is experimentally verified. The structure parameters, permeability, filtration performance and mechanical properties of new anticlogging filtration material and two traditional nonwoven geotextiles are tested and compared. The relation between needle-punching density and nonwoven geotextiles properties is also discussed. The experimental results prove that the new filtration material possesses better permeability and anticlogging properties and mechanical strength and the development of this new filtration material is more significant.
Keywords/Search Tags:needle-punched nonwoven geotextile, anticlogging filtration material, permeability, filtration performance, mechanical properties
PDF Full Text Request
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