Journal of Natural Disaster Science
Journal of Natural Disaster Science Vol.22, No.2, 2000
Liquefaction and the Steady State of Weathered Granitic Sands Obtained by Undrained Ring Shear Tests:
A Fundamental Study of the Mechanism of Liquidized Landslides
(Received for 1 Aug., 2000 and in revised form 9 Jan., 2001)
Abstract
Liquidized landslides have caused many disasters because of their high mobilities and long travel distances. The 1995 Takarazuka Golf Course landslide is a typical liquidized landslide with a runout of 180 meters. A series of undrained speed-controlled ring shear tests and another series of undrained strain-controlled triaxial compression tests were conducted on weathered granitic sands to determine the conditions under which liquidized land-slides are generated in order to investigate the process of liquefaction and shear behavior in the steady state as key phenomena in such landslides. Test results showed that liquefaction was generated in loose to dense specimens in the ring shear tests, whereas in triaxial compression tests liquefaction occurred only in loose specimens. The apparent friction angles in the steady state obtained by the ring shear tests after grain crushing terminated were smaller than the values for the Takarazuka Golf Course landslide. Because that landslide showed a clear shear surface, grain crushing in that surface must have been complete or almost complete. The direct shear state with large shear displacement reproduced in the ring shear tests corresponds to the state of shearing in the sliding surface of the landslide. The small apparent friction angles obtained in the ring shear tests therefore provide a good understanding of the high mobility of liquidized landslides.
Key words
landslide, ring shear test, liquefaction, steady state, collapse, triaxial compression test.