The soil water retention curve (SWRC) is usually measured by the axis translation technique (ATT), assuming a specimen thickness of a few centimetres. Usually, this assumption is unquestionable to ensure the representative elementary volume (REV). However, such an assumption cannot always be conserved with coarser soil regarding the local heterogeneities generated by larger pore sizes. In addition, the authentic SWRC is supposed to be the soil moisture profile above the phreatic surface. Those issues, therefore, raise concerns about the scale effects in SWRC. With an aim to investigate them, this work compared the primary drainage SWRCs of coarse, medium and fine sand measured by the standard hanging column and full-scale soil column (150 cm). The soil moisture profile at the final drainage stage was detected using the spatial time domain reflectometry (spatial TDR) technique with a presentation of sensor calibrations and validations. The observations showed discrepancies between SWRCs given by two methods in terms of air entry value (AEV) and slope of SWRC but agreements on residual moisture content. Moreover, such differences could be alleviated with the soil becoming finer and better graded. Finally, the physical reasons are discussed, referring to local heterogeneity and pressure gradient changes on the top boundary. In conclusion, the full-scale soil column test can be utilised to avoid scale effects, despite demanding high costs and massive labour efforts. Also, a shorter soil column incorporating point-wise suction and moisture sensors in prior studies could be an alternative solution.

假设样品厚度为几厘米，土壤保水曲线 (SWRC) 通常通过轴平移技术 (ATT) 测量。通常，这一假设无疑可以确保具有代表性的基本体积 (REV)。然而，对于较大孔径产生的局部异质性，这种假设并不总是适用于较粗糙的土壤。此外，真正的 SWRC 应该是潜水面以上的土壤水分剖面。因此，这些问题引发了对 SWRC 规模效应的担忧。为了研究它们，这项工作比较了标准吊柱和全尺寸土柱（150 cm）测量的粗、中、细砂的初级排水SWRC。最终排水阶段的土壤水分剖面使用空间时域反射仪（空间 TDR）技术检测，并提供传感器校准和验证。观察结果表明，两种方法给出的 SWRC 在空气进入值 (AEV) 和 SWRC 斜率方面存在差异，但在残余水分含量方面存在一致性。此外，随着土壤变得更细和更好的分级，这种差异可以得到缓解。最后，讨论了物理原因，参考了顶部边界的局部非均质性和压力梯度变化。总之，尽管要求高成本和大量劳动力，但可以利用全尺寸土柱测试来避免规模效应。还，