Journal
CANADIAN GEOTECHNICAL JOURNAL
Volume 54, Issue 5, Pages 664-673Publisher
CANADIAN SCIENCE PUBLISHING
DOI: 10.1139/cgj-2016-0171
Keywords
debris flow rheology; vane-measured rheometer; loose sands; viscosity; yield stress
Funding
- Public Welfare and Safety Research Program through the National Research Foundation of Korea - Ministry of Education [2012M3A2A1050977]
- Smart Civil Infrastructure Research Program - Ministry of Land, Infrastructure, and Transport of the Korean government [13SCIPS04]
- Korea Agency for Infrastructure Technology Advancement
- Brain Korea 21 Plus
- National Research Foundation of Korea [2012M3A2A1050977] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
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The objective of this study was to investigate the rheological properties of loose sands subjected to upward flow by using a vane-type rheometer that controlled upward flow in the loose sand specimens. Various hydraulic gradients (i.e., i = 0-2.0) were applied to loose sands. The rheological properties of the loose sands, such as yield stress and viscosity, were determined based on the Bingham and Herschel-Bulkley models. The experimental results showed that the flow behavior of loose sand samples exhibited a shear thickening when the Herschel-Bulkley model was applied (i.e., nondimensional flow index n > 1) and exhibited a Bingham-like within a limited shear rate range (i.e., 1 similar to 30 1/s). The latter is clearly shown for a relatively high shear rate. As the hydraulic gradient was increased, the flow characteristics were close to the Bingham fluid. Yield stress showed a tendency to decrease linearly as hydraulic gradient was increased. However, the viscosity of the loose sands maintained a constant value irrespective of hydraulic gradient. The test results indicated that the pore fluid pressure resulting from upward flow in a soil sample affects yield stress, which contributes to the initiation of debris flow mobilization. As a result, it was possible to estimate the rheological properties of soil at the condition of liquefaction (critical hydraulic gradient), or initial occurrence of debris flow.
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