Viscosity determination of soil in plastic and viscous liquid states for elucidating mudflow behavior

Abstract

The transformation of soil from a plastic state into a VISCOUS liquid state is primarily caused by changing the water content of the soil mass. As the water content increases, the soil mass gradually starts to behave like a viscous liquid. In spite of viscosity being a key parameter to the behavior of mudflows, there have no datasets of soil viscosity changes successfully measured continuously as they move from plastic to viscous liquid states. The aim of the current research "is to design a new device to overcome this difficulty. Based on the trap door principle formulated by Terzaghi (1943) and the Bingham model, a new device called the Flow Box was designed. The governing equation of the Flow Box was derived in this research in order to obtain the relationship between initial viscosity and liquidity index. In this study, the viscosities in both plastic and viscous liquid states were clearly defined by the Flow Box Test. The expected decrease in initial viscosity was followed by an increase in liquidity index, which corroborated with the test results. The initial viscosity readings with the results of other similar research and the case study of the Maokong mudflow was also validated.