基于孔隙尺寸的粗粒土渗透系数计算方法研究

基于颗粒极限堆积状态下的平面孔隙直径和土体粒径组成,采用颗粒随机抽样组合获得了土体各孔隙直径百分含量,并进一步得到了土体最密实和最疏松状态下孔隙直径累计分布曲线CSD-D、CSD-L。通过土体实际相对密度的线性内插方式获得了土中孔隙直径累计分布曲线CSD-R,并得到相应平均孔隙直径Dmc,根据粗粒土渗透试验结果建立了渗透系数K与Dmc关系的经验公式。研究表明:CSD-R曲线同时考虑了颗粒级配和密实度对土中孔隙尺寸分布的影响,所确定的经验公式近似满足多孔介质渗流理论中渗透系数与渗流孔隙呈二次正相关性的规律。对比相关试验结果认为,该方法具有较高准确性,适用于不均匀系数Cu7且有效粒径d109.6 mm的粗粒土渗透系数估算。

Permeability coefficient calculation of coarse grain soil based on pore-size distribution technique

Based on the plane pore-size and soil gradation in limited particle packing configuration, we adopt equiprobable random sampling to obtain several pore diameter percentage composition, and furthermore obtain the pore diameter accumulative distribution curves, the CSD-D and CSD-L, under the densest and loosest state of soil.Therefore, the actual pore diameter accumulative distribution curve CSD-R is worked out by using linear interpolation of soil relative density, so was the mean pore size.Finally, an empirical formula between permeability coefficient K and is established by plenty of permeability tests.The research indicates that the CSD-R curve considers the influence of particle gradation and density on pore size distribution simultaneously.The empirical formula is in agreement with the seepage law of porous medium theory that the permeability coefficient and the pore-size have a quadratic positive correlation.Compared with the test permeability coefficient of some coarse grained soil samples, the calculated value has a high accuracy, which is applicable to coarse grained soil whose uniformity coefficient Cu is less than 7 and effective diameter d10 is less than 9.6mm.