| Abstrakt: |
The slope failure and the debris flow at Chandmari and Sichey within the city of Gangtok in Sikkim, India, have been numerically analyzed using the distinct element method. The published data on the failure surface and the extent of the debris flow, which followed a 5-h, 210-mm rainfall event in 1997 at Chandmari, have been used to verify the adopted methodology. The numerical simulations have revealed that the runout distances predicted for the landslide are in agreement with the actual ground observations. After a satisfactory simulation of the Chandmari landslide, the instability and the debris flow at Sichey, located on the backside of the same mountain, were studied. The results indicated that a collapsed building noticed during a 2019 field visit to Sichey is located within the predicted failure surface. The debris flow after the ground saturation originates from two distinct parts of the Sichey slope, located near the toe and the crown of the potential failure surface. The debris flow from the lower slope failure, near the toe of the critical slip surface, has a longer runout distance and higher velocity than the debris flow from the upper slope failure near the crown of the critical slip surface. Due to a broad and relatively flat road bench located at the middle portion of the failure surface, these two distinct debris flows might not get a chance to merge to form a major destructive force entirely, and thus, the locality in the down slope might escape a total inundation. [ABSTRACT FROM AUTHOR] |
