无纺土工织物作为一种反滤材料，在工程中常受土体作用产生平面双轴拉应变，导致织物孔径变化。基于无纺织物空间网络孔径模型，改进Rawal公式中织物孔径结构总层数的算法，并提出等双轴拉伸下织物孔径分布曲线的解析解。利用自主研发的双轴拉伸仪，将两种针刺无纺织物等双轴拉伸至应变为3%、5%、10%，采用应变控制下的干筛法，进行织物孔径分布曲线测试。将解析解与试验结果进行对比分析，解析解孔径值偏大，所得解析曲线与测试曲线对于较薄织物吻合更好。研究结果表明，随着双轴拉应变的增加，无纺织物孔径增大，其特征孔径O95、O50、O30都近似与拉伸应变呈线性变化关系。

Nonwoven geotextile is used in engineering as filter materials. When the geotextile is subjected to biaxial tension, the pore size of geotextile can be changed. Based on a 3D pore network model for the nonwoven geotextile, the method for calculating the number of structural layers in Rawal’s formulation is improved and a theoretical solution is proposed for the pore size distribution of nonwovens under equal biaxial tension. Two geotextiles are uniformly stretched in bi-directions to strains of 3%, 5% and 10%, respectively, using a self-developed bi-directionally stretching machine, and the pore-size distributions of the stretched geotextiles are determined under strain-controlled condition using the dry sieving method. By comparing the theoretical solutions and the measurements, it is shown that the theoretical method overestimates the pore sizes, and yields more reasonable results for the thinner geotextiles. In addition, the pore sizes increase with the biaxial tensile strain，and the characteristic opening size O95, O50, and O30 increase approximately linearly with the tensile strain.