Soil-Water Characteristic Curves and Fitting Models of Collapsible Loess: A Case Study of Lanzhou, China

Abstract

The soil-water characteristic curve (SWCC) is an important hydrodynamic representation of soil and the basis for studying the water content of collapsible loess. The objectives of this study were to determine the water holding capacity of collapsible loess and the best fitting model of SWCC. We selected representative samples of collapsible loess in Lanzhou and measured the SWCCs. The SWCCs for soil samples varied with bulk density and particle size. The shapes were the same, but the volumetric water content (VWC) decreased as the suction increased. The suction of different soil layers tended to first decrease rapidly, then decrease more gradually and finally stabilize with VWC. The fitted VWC for the VG model was closer to the measured content, and the accuracy of the model was high. The VG-M (1-1/n, n) model was the best of the six models tested and was selected as the optimal model for fitting SWCCs, which will provide a theoretical basis for the accurate fitting of data of collapsible loess.