基于滤纸法的非饱和渗透性曲线测试

渗透性曲线是反映非饱和土中水分运移的重要参数,瞬态剖面法是测定渗透性曲线的常用方法。将滤纸法应用于传统的瞬态剖面法,设计了一种土柱装置,用于测定土体的渗透性曲线。该装置包括上部能够持续给水的供水系统及下部由带环刀的土样与滤纸叠置而成的土柱。在水分下渗过程中,定期测量土样与滤纸的质量以获得土柱的含水率剖面与水头剖面,根据所测数据计算得到土-水特征曲线和渗透性曲线。用此方法测得甘肃正宁马兰黄土与第1层古土壤的渗透性曲线和土-水特征曲线,该方法测量的吸力范围大,为1~1^05 kPa,渗透系数范围在10^-5~10^-13 m/s。用常见的统计预测模型预测了土体的渗透性曲线,并与实测曲线对比发现小吸力范围预测值与实测值相符,大吸力范围预测值偏差较大。

Measurement of unsaturated permeability curve using filter paper method

The permeability is an important parameter which reflects the moisture movement in unsaturated soil.In this paper,a soil column device is designed combining instantaneous profile method and filter paper method to determine permeability function.The device includes a continuous water supply system at the upper part and a soil column composed of soil sample with a cylinder and filter paper at the lower part.During the infiltration,the mass of soil samples and filter papers are measured to determine the water content profile and hydraulic head profile.Then the soil-water characteristic curve and permeability curve are calculated by these data.The Malan loess and the first layer of paleosol from Zhengning,Gansu province are tested.The results show that the method covers a wide range of suction from 1 to 10^5 kPa,and permeability coefficient range of 10^-5-10^-13 m/s.This method is simple,inexpensive,and available for both intact and remolded soil.Moreover,several common statistical permeability models including Childs&Collis-Geroge model,Fredlund model,van Genuchten model,and Priesack&Durnerare model are used to predict the permeability curve of the two soils.The results show that the predicted results are consistent with the measured results in low suction range,while they are not in high suction range.