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| DOI：10.13522/j.cnki.ggps.2020128 |
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| The Relationship Between Hydraulic Properties and Pore Structure of Geotextile Used in Subsurface Drainpipe |
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XIE Zhongyi, LI Mingsi*, HAN Han, LAN Mingju
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College of Water Resources and Architectural Engineering, Shihezi University, Shihezi 832003, China
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| Abstract: |
| 【Objective】Geotextiles are often used in subsurface drainage by wrapped around the drainpipe buried in the subsurface as a filter. Their pore structure and hydraulic permeability play an important role in operation of the drainage system. The objective of this paper is to investigate the relationship between hydraulic properties of the geotextiles and their microscopic pore structure.【Method】We compared three types of geotextiles: perforated short-fibber geotextile, polyester-filament geotextile and super-thin geotextile, with 10 varieties. Microscopic structure and permeability of each geotextile under both saturated and unsaturated conditions and in different directions were measured in the laboratory from microscopic observation, permeability test rig, water drainage, as well as the improved funnel-tension plate assembly. We proposed a model to estimate the pore structure and linked it to hydraulic properties of the geotextiles.【Result】①Planar and volumetric porosity of all geotextiles increased as their density decreased. As the density increased, the porosity of the short-fibber and polyester-filament geotextiles in the transverse direction increased while that of the super-thin geotextiles increased first followed by a decline. ②The higher the porosity of the geotextiles in the longitudinal direction was, the more permeable they were in the transverse direction. ③Saturation of the short-fibber and polyester-filament geotextiles decreased when they were placed from 0° with the horizontal direction to 90° with the horizontal direction; the ability of the geotextiles to hold water was proportional to their volumetric density. Under the same saturation, there was a positive correlation between capillary pressure and the thickness of the first two types of the geotextiles.【Conclusion】The permeability and ability of the geotextiles to hold water are inversely proportional to their porosity in the longitudinal direction. Our results have implications for selecting geotextiles in designing subsurface drainage systems. |
| Key words: subsurface drainpipe; nonwoven geotextiles; pore structure; permeability; water holding capacity |
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