ORIGINAL RESEARCH
Experiment and Modeling of Soil-Water
Characteristic Curve of Unsaturated Soil
in Collapsing Erosion Area
Weiping Liu1,2, Xiaoyan Luo1,3, Mingfu Fu1, Jinsong Huang1,2
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1School of Civil Engineering and Architecture, Nanchang University, Nanchang 330031, China
2ARC Centre of Excellence for Geotechnical Science and Engineering, The University of Newcastle,
Callaghan, NSW 2308, Australia
3Jiangxi Science and Technology Normal University, Nanchang 330013, China
Submission date: 2016-04-11
Final revision date: 2016-07-19
Acceptance date: 2016-07-19
Publication date: 2016-11-24
Pol. J. Environ. Stud. 2016;25(6):2509-2517
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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.