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有纺土工织物的孔径特征是反滤设计的重要指标。工程中有纺织物常处于不等轴双向受拉状态,引起孔径变化,导致织物反滤性能失效。采用数字图像法测试了不等轴双向拉应变下,3种条膜有纺织物的孔径参数变化,包括孔洞长宽比、开孔面积率、等效孔径(O95)等。对比经纬向应变比2∶1,3∶1,4∶1对试验结果的影响,根据孔径特征变化规律,揭示不等轴双向拉伸引起孔径变化的机理。运用图像法试验结果,验证已推导的双向应变下开孔面积率及孔径理论解。试验结果表明:开孔面积率、等效孔径(O95)均随双向拉应变的增大而增大。纬向应变相同时,经纬向应变比越大,孔洞形态(即孔洞长宽比)变化越大,开孔面积率及孔径变化的斜率越大。理论解较好地预测了开孔面积率及孔径的变化率及数值,孔径参数与双向拉应变呈现近似线性关系。但理论解的孔径计算以孔面积为指标,无法考虑应变比造成的孔形态变化对反滤作用的影响。
Aperture characteristics of woven geotextiles are important indicators of filter design. Textile projects often in the unequal two-way tension state, causing changes in pore size, resulting in failure of fabric filtration performance. Using the digital image method to test the change of the aperture parameters of the three kinds of strip woven fabrics under unequal-axis and biaxial tensile strain, including the aspect ratio of holes, the area of opening area, the equivalent aperture (O95) and so on. Comparing the effect of warp and weft strain ratio of 2: 1, 3: 1, 4: 1 on the test results, the mechanism of the change of pore diameter caused by the biaxial stretching of the equiaxed billet was revealed according to the variation of the pore size characteristics. The results of the image method are used to verify the deduced area ratio of aperture and the theoretical solution of aperture under bidirectional strain. The experimental results show that the open area ratio and the equivalent diameter (O95) increase with the increase of the biaxial tensile strain. When the zonal strain is the same, the larger the ratio of warp and weft, the larger the change of the hole shape (ie, the aspect ratio of the hole), and the larger the slope of the area ratio and the hole diameter change. The theoretical solution better predicts the rate of open area and the rate of change of aperture, as well as the numerical value. The parameter of the aperture shows an approximately linear relationship with the biaxial tensile strain. However, the calculation of the pore size of the theoretical solution takes the pore area as an index and can not consider the influence of the pore shape change caused by the strain ratio on the filtration effect.