滤纸法测定膨胀土总吸力试验及基质吸力预测研究

采用滤纸法测定膨胀土体吸力时,滤纸与土体表面距离不同所测得的滤纸含水率也不一样,获得的总吸力亦不相同。为此采用滤纸法开展了不同距离下的膨胀土总吸力测定试验,获得了不同距离条件下滤纸含水率的变化规律。干密度较小时,滤纸含水率随距离的增大呈现"减小-增大-减小"的规律;干密度较大时,滤纸含水率随距离的增大逐渐减小,最终趋于稳定。距离为3cm时所测得的吸力离散程度较小,可作为测定土体总吸力的标准距离。根据总吸力-距离关系式,通过引入伪基质吸力的概念,计算得到伪基质吸力,并与相应的真基质吸力进行比较。结果表明:不同干密度及含水率下的膨胀土真基质吸力与伪基质吸力之间存在良好的线性关系。此法可为测定现场土体基质吸力提供新的思路。

Tests on Total Suction Measurement of Expansive Soil Using Filter Paper Method and Prediction of Matrix Suction

Using filter paper method the measured water content is different due to the different distances between filter paper and soil surface, and the relevant soil suction is also different. For this purpose, tests were carried out to measure the total suction of expansive soil under different distances between filter paper and soil surface, and the relationship between water content of filter paper and distance was obtained. When the dry density of soil is small, the water content of filter paper decreased firstly, then increased and finally decreased with increasing distances. When the dry density is large, the water content of filter paper decreased with increasing distances and then remained stable. The dispersion degree of soil suction is lesser at a distance of 3cm than at other distances; hence, this distance could be regarded as a standard distance for measuring soil suction. The total suction-distance relationship was established by introducing the concept of pseudo matrix suction, and the relevant pseudo matrix suction was obtained. The true matrix suction has a linear correlation with the pseudo matrix suction under different dry densities and water contents. This method can provide a new idea for the determination of field soil matrix suction.