The study of unsaturated behavior of soils pivots around the relationship between soil suction and the amount of water content present in the soil mass, which is termed as soil–water retention curve (SWRC). The drying SWRC is generally determined by neglecting the volume change behavior of the soil for low plastic soils. Such a procedure is bound by an inherent assumption that the soil exhibit zero or negligible volume change and can lead to approximations in important SWRC parameters, including saturated volumetric water content, residual water content, and fitting parameters, which are essential for the estimation of unsaturated hydraulic characteristics of the soil. This study deals with the determination of SWRC parameters for a range of soils starting from non-plastic to high plastic soils, with and without considering volume change characteristics. For this purpose, the SWRC of six different natural soils were experimentally measured using a miniature tensiometer (T5) and a dew point potentiometer (WP4C), while the VSC of the used soils were measured using the balloon method. Efforts were made to critically understand the influence of no volume change assumption on the SWRC parameters, unsaturated hydraulic conductivity function, and flow of water through 1D soil column. The experimental results indicated that the no volume change assumption underpredicted the water retention curves of low plastic soils, and this error in SWRC increases with the soil plasticity. The measured VSC of the used soils further revealed that there could be a range of saturated volumetric water content (VWC) depending on the initial state of the soil sample, which also influences the sensitivity of the SWRC parameters. Therefore, the present study proposed a new methodology to determine unambiguous SWRC (in terms of VWC-suction) for a particular soil type combining both the measured VSC data and SWRC data. Based on the obtained results, it was recommended that the details of VSC must be incorporated along with the measured SWRC data for soils having plasticity and clay content higher than 15 and 11%, respectively.

对土壤非饱和行为的研究围绕着土壤吸力与土壤团块中水分含量之间的关系而展开，这被称为土壤水分保持曲线（SWRC）。对于低塑性土壤，通常通过忽略土壤的体积变化行为来确定干燥SWRC。这样的程序受一个固有的假设所约束，即土壤的体积变化为零或可忽略不计，并且可以导致重要的SWRC参数（包括饱和体积水含量，残留水含量和拟合参数）的近似值，这对于估算不饱和度是必不可少的。土壤的水力特性。这项研究致力于确定从非塑性土壤到高塑性土壤的各种土壤的SWRC参数，考虑和不考虑体积变化特征。为此，使用微型张力计（T5）和露点电位计（WP4C）对六种不同天然土壤的SWRC进行了实验测量，而使用气球法测量了所用土壤的VSC。努力批判性地了解了无体积变化假设对SWRC参数，非饱和导水率函数和水通过一维土柱的流量的影响。实验结果表明，没有体积变化的假设会低估低塑性土壤的保水曲线，而SWRC中的误差会随着土壤可塑性的增加而增加。对用过的土壤进行测量的VSC进一步表明，取决于土壤样品的初始状态，可能存在一定范围的饱和体积水含量（VWC），这也影响SWRC参数的敏感性。因此，本研究提出了一种新的方法来结合测量的VSC数据和SWRC数据确定特定土壤类​​型的明确SWRC（就VWC抽吸而言）。根据获得的结果，建议对于塑性和黏土含量分别高于15％和11％的土壤，必须将VSC的详细信息与测得的SWRC数据结合在一起。本研究结合测量的VSC数据和SWRC数据，提出了一种确定特定土壤类​​型的明确SWRC（就VWC抽吸而言）的新方法。根据获得的结果，建议对于塑性和黏土含量分别高于15％和11％的土壤，必须将VSC的详细信息与测得的SWRC数据结合在一起。本研究结合测量的VSC数据和SWRC数据，提出了一种确定特定土壤类​​型的明确SWRC（就VWC抽吸而言）的新方法。根据获得的结果，建议对于塑性和黏土含量分别高于15％和11％的土壤，必须将VSC的详细信息与测得的SWRC数据结合在一起。