Investigation of Relation between Soil Water Characteristic Curve and Consolidation by Sand Box Test and Hysteresis Modeling
Date Issued
2007
Date
2007
Author(s)
Ke, Kai-Yuan
DOI
zh-TW
Abstract
The soil volumn (or the porosity) would change with respect to natural event such as seasonal variation, precipitation, earthquake, or human activities, such as irrigation, pumping, and structure building. Two kinds of previous studies on this field:(1) the consolidation or compaction due to stress changed in the soil by natural enents or human activities, while the the water retention curve(WRC) is considered to have fixed parameters; (2) the relation between the change of porosity and hydraulic parameters of soil, because the hydraulic properties, such as the saturated hydraulic conductivity or parameters of water retention curve, of the soil must be somewhat changed due to the change in soil volume or porosity. But this kind of research barely discussed the soil water movement with respect to the change of hydraulic parameters.
The purpose of this study is to find out the interactive mechanism between change of porosity, hysteresis and soil water movement. This research considers that the change of volumn or porosity in the unsaturated soil will directly influence the behavior of the water retention curve, and thus the mechanism of soil water movement.
This study finds out the linear relation between the WRC parameters and the porosity of quartz sand with a WRC sand box test. Besides, a recycling water level sand box test is also conducted to study the interactive relation of water content, soil water tension and soil volumn by controlling the boundary condition to similuate the groundwater change. In the mean time, a consolidation process followed by a swelling process is found during drainage.
In the infiltration simulation, while the porosity becomes smaller due to compaction, higher water content appears near the top boundary, and the wetting front depth decreases with the porosity. When top boundary flux is set to zero, the depth of the highest water content decreases with porosity. Besides, no matter the top boundary is zero flux or non-zero flux, the deepest wetting front always occurs in the soil with the highest porosity.
In addition, the result of the recycling water level sand box test is verified with a hysteresis model. The results show that the repeated water level change will lead to the change of property of water retention curve and soil consolidation, indicating that the change of water content and soil water tension is caused by hysteresis, as well as change of porosity.
Subjects
壓密
砂箱實驗
遲滯現象
孔隙率
consolidation
sand box test
hysteresis
porosity
Type
thesis
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