Abstract

The large landslide is a potential hazard for residential areas, traffic infrastructure, terraces, and power transmission lines in the northern mountainous region. To develop a basic understanding of the large landslide in this region, a statistic analyze of large landslides has been performed. Through aggregate statistics of 8,304 landslide, the result shows that the statistical distribution of occurrence frequency of the logarithm of the landslide volume follows the normal distribution and the limit on the large landslide volume (95 % confidence level) at 4,500 m3. The large landslide is mostly of the translational and complex landslide. The most dangerous slope surface is located on the discontinuity between the material boundary or the tectonic fracture zones. The characteristics of type, slope surface, terrain surface deformation, displacement stages, movement speed of the large landslide are significantly different from those of the shallow landslide. Various works were carried out on the site, i.e., measuring the dimension of the landslide slope (width, length, height, sliding thickness and angle); examining the characteristics of the sliding surface and slope strata (hydro-geological conditions, dip angle, fractures); and interviewing the witnesses and local residents. Especially, topographical features of the landslide area were carefully examined with aerial photos taken by an unmanned aerial vehicle (UAV). The main characteristics are more clearly seen in the fact of large landslide such as: Tan Son market landslide, Nam Bung landslide, Che Cu Nha landslide, Ma Thi Ho landslide, Thac Khanh landslide, Sang Tung landslide…

Introduction

In Vietnam, landslide is a common phenomenon, especially in the northern mountainous provinces. Landslide occurs especially seriously in the rainy season, often causing great damage, not only directly affecting infrastructure works but also threatening human life. In particular, the large landslide occurs often causing damage that cannot be quickly remedied. Landslide destroys the original slope, changing the shape of the slope to create a new terrain. With a wide range of influence, the large landslide is also a source of material addition to the debris flow and flash flow.

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