Rapidly Determining the Unsaturated Permeability by Transient Two-Steps Outflow Experiment
Numerous methods have been developed to measure the unsaturated permeability in multi-step outflow experiments. Silicon micro-powder (SMP) and Guangxi Guiping clay (GGC) have been conducted by transient outflow methods in this paper. The water release upon two-steps increase in matric suction. For each step of the experiment, the water outflow from the soil specimen is weighed in real time in order to determine the change of the water content in the specimen. As a gas pressure is exerted, the difference of the matric potential between the transient water content curve (TWCC) and the soil water retention curve (SWRC) at the same water content is calculated. This difference is considered to have the potential to drive the flow of pore water. Then, the unsaturated permeability can be calculated by using Darcy’s law. This two-steps measurement method agrees with the Gardner outflow analysis method (1956), which have the same ranges of variation for unsaturated permeability. Additionally, the test time is greatly reduced, and generally takes 10 days.
KeywordsUnsaturated soil Two-steps outflow experiment Unsaturated permeability
This research was funded by the National Natural Science Foundation of China (No. 51479023).
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