Determination of geotechnical and rheological properties of clay-rich soils in the Ullueng Basin, East Sea
Abstract
Submarine landslides are easily identified in the Ulleung Basin, East Sea, Korea. Common landslide types are slumps, slides, rockfalls, debris flows and turbidites. Little is known of the landslide characteristics in the Ulleung Basin in terms of the transition from slide to flow. This tansition is very important to understand the high mobilization of landslides and secondary effect of geo-hazards. In the slope stability and flow dynamics, the geotechcial and rheological parameters obtained from the field and laboratory testing are desirable rather than the values obtained from a trial and error method. However empirical correlations are commonly used as an input parameter in the back-analyis of landslide mobilization. There is very little information about geotechnical and rheological characteristics of the Ulleung basin sediments for eastimating the landslide hazards. Appropriate parameter for landslide and debris flow simulation will be suggested for observed past landslide events in the Ulleung Basin. Geotechnical test results including consolidation will be also discussed compared with other natural clays. In the failure stage, the residuatl shear strength determined from large-scaled ring shear testing is considered with different drainage and shearing methods; in the post-failure stage, the yield strength determined from rate-controlled rheometric testing is used to link the transition from solid to liquid in landslide motion. Ring shear testing is done for clay-rich soils with different drainage and shearing speed ranged from 0.01 to 100 mm/sec. For rheological tests, two samples were condsidered : (i) clay-rich sediment taken from the Ulleung Basin and (ii) natural clay, called the Busan clay, taken from the deltaic plain area in the south part of south Korea. Rheological characteristics are examined in response to stress and rate-control mode in rheometer MCR52 model (Anton-Paar, Austria). Salinity dependent rheological characterisitcs will be also discussed as a comparison between Ulleung Basin and Busan clays. The correlation between yield strength and viscosity is proposed; it can be useful in future flow dynamics in the Ulleung Basin. Preliminary testing results show that there are large difference between strength parameters obtained from ring shear and rheometric tests. The strength parameters can change by a factor of 3-5.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMNH43E1100J
- Keywords:
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- 4304 Oceanic;
- NATURAL HAZARDSDE: 4313 Extreme events;
- NATURAL HAZARDSDE: 4341 Early warning systems;
- NATURAL HAZARDSDE: 7215 Earthquake source observations;
- SEISMOLOGY