Experiment and Modeling of Soil-Water Characteristic Curve of Unsaturated Soil in Collapsing Erosion Area

Abstract

Soil erosion tends to occur with rainfall runoff, thus leading to grave soil and water loss. An increase of water content in soil caused by rain makes the loss of matrix suction and the decrease of shear strength obvious, and will promote soil erosion. The soil-water characteristic curve (SWCC) can be used to describe the relationship between the water content and the matrix suction in unsaturated soil. For this paper we studied the SWCCs of the granite residual soils in a collapsing erosion area in Jiangxi Province, China. A GEO-Experts pressure plate extractor was used to measure SWCCs for soils with different dry density, grain size, drying and wetting cycles, and lime content. The initial dry density has a significant impact on SWCC. With increasing dry density, the suction was decreased for the same water content. The larger the grain size, the greater the suction value for the same volumetric water content. Under the same suction, the volumetric water content decreases as the lime percentage increases and water stability improves. SWCCs of the drying and wetting cycle demonstrate the hysteresis phenomenon. The area of the hysteresis loop decreased with the increase of the dry density and drying and wetting cycle number. It also became small when the soils were mixed with lime. In this paper, the Van Genuchten model, the Fredlund and Xing model, and the Gardner model were used to fit the experimental data of SWCCs. The presented fitting parameters show that the residual sum of squares is less than 0.002. All the experimental data fit well to three models for SWCC. The results indicated that the simulated value of the Gardner model does provide best agreement with the measured value. These results will provide an important basis for the further study of the soil collapsing erosion process and soil cover design.

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

“…Phoon [10] demonstrated that a lognormal random vector is suitable to model the curve-fitting parameters of the SWCC. Liu [11] reported that the Gardner model was better than the models of van Genuchten, Fredlund and Xing for an area erosion of collapsible soil near the city of Ganzhou. Zhao [12] believed that the fitting accuracy for sandmulched land was higher for the van Genuchten than the Brooks Corey model.…”

Effect of Substrate Ratio on Soil’s Water-Holding Capacity and Shrinkage

“…It is an important parameter for simulating the movement of moisture and the transport of solute within the soil, and plays an important role in studying and evaluating the water-holding characteristics of soil and the solute transport in soil's moisture movement [9][10][11][12][13]. The moisture characteristic curve of soil is mainly affected by soil's texture, bulk density, especially soil's structure and many other factors [14][15][16]. At present, it is difficult to theoretically calculate the relationship between the water potential and water content of soil.…”