Rheology of marine sediments at the eastern margin of the Korea Peninsula and its implications for submarine debris flow mobility

To estimate the debris flow runout distance and its velocity, the geotechnical and rheological parameters of marine sediments are requested. To obtain the yield stress and viscosity as rheological properties, steady state and oscillatory shear rheology were conducted for marine sediments taken from the Ulleung Basin, East Sea. In general, marine sediments act as a yield stress fluid, such as a non-swelling materials. For the materials examined, yield stress and viscosity are sensitive to the change in volumetric concentration of sediment and salinity. In particular, at the same liquid limit, especially for the liquid limit state, the value is unique; however, when the liquidity index increases, the difference of rheological properties are large. According to the test results, the Bingham and bilinear yield stresses in controlled shear modes ranges approximately from 100 Pa to 4000 Pa. The large gap is due to the imposed shear loads: e.g. steady state and oscillatory shear loads. One of large difference is reached to the twice. Since the yield stress and viscosity affect the runout distance and peak velocity of debris flow materials, the difference create different geomorphological characteristics. For the debris flow simulation, Massmov2d is used. In this presentation, the debris flow characteristics depending on geotechnical and rheological parameters will be discussed.