扬州沿运灌区暗管排水土工布外包滤料的水力性能试验研究

农田暗管排水系统建设是提高农业机械化作业效率的有效措施之一.土工布作为排水暗管外包滤料时,需要具有良好的透水性能和抗淤堵能力.文中以扬州段沿运灌区为例,针对当地土壤中粉粒含量较高,土工布外包滤料筛选困难等实际问题,参考相关技术准则,选用2种开孔率和厚度不同的土工布进行了水力渗透试验,并与传统的河砂反滤材料进行了对比,筛选出适合当地土壤的土工布外包材料.研究结果显示,所选用的2种土工布透水性能存在较大差异,其中厚度较大(0.41 mm)、孔径较小(180 μm)的土工布A的透水性能较好,渗透系数为初始值的54.1%,高于河砂滤层的46.1%,而厚度为0.35 mm、孔径为227 μm的土工布B渗透系数仅为初始值的30.2%.相比于土工布B,土工布A具有更好的抗淤堵能力,长期使用后淤堵率比土工布B低16%.通过对土工布表面形成的、透水性较低的滤饼分析发现,土工布B不但自身发生了较大程度淤堵,其表面形成的滤饼较为密实,是影响其渗透性能的直接原因.

Experimental study on hydraulic performance of subsurface drainage geotextile envelope in Yangzhou Yanyun Irrigation District

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.