Abstract：The construction of farmland subsurface pipe drainage system is one of the effective measures to improve the efficiency of agricultural mechanization operations. When the geotextile is used as an envelope material for the subsurface drainage pipe, it needs to have a good permeability and anti-blocking ability. In this paper, taking the irrigation area along the Yangzhou section as an example, in view of the high content of powder particles in the local soil, the actual problem of difficult screening of the geotextile envelope material, referring to the relevant technical guidelines, two kinds of geotextiles with different opening ratios and thicknesses were selected for hydraulic permeability tests, and compared with traditional river sand filter materials, so as to the geotextile envelope materials suitable for the local soil were selected. The research results show that the water permeability of the two selected geotextiles is quite different. The geotextile A with a larger thickness(0.41 mm)and a smaller pore size(180 μm)has better water permeability, and the permeability coefficient is 54.1% of the initial value, which is higher than 46.1% of the river sand filter layer. The permeability coefficient of geotextile B with a thickness of 0.35 mm and a pore size 227 μm is only 30.2% of the initial value. Compared with geotextile B, geotextile A has better anti clogging ability, and the silting rate after long-term use is 16% lower than geotextile B. Through the analysis of the low permeability filter cake formed on the geotextile surface, it is found that not only the geotextile B itself has a large degree of silting, but also the filter cake formed on its surface is relatively dense, which is the direct reason that affects the permeability of the geotextile.
