Abstract
The Great Wenchuan Earthquake of Ms 8.0 in Richter scale on 12 May 2008 caused the formation of 34 large and numerous smaller landslide dams. Hongshihe Landslide Dam is one of the large-scale dams. The erodibility of fresh landslide deposits plays an important role in evaluating the breaching process of such landslide dams due to overtopping. A landslide dam typically comprises freshly deposited mass of heterogeneous, unconsolidated or poorly consolidated earth materials and is vulnerable to overtopping failure. The landslide deposits are usually broadly graded with particle sizes ranging from clay to boulders. Moreover, their grain size distributions are highly heterogeneous along depth and along the run-out direction of landslide debris. Due to the variation of soil properties, the soil erodibility also varies significantly along the run-out direction and depth. This paper describes a series of field jet index tests conducted at two landslide dams shortly after the earthquake to investigate the erodibility of freshly deposited landslide soils. The basic soil parameters (i.e., grain-size distribution, bulk density, water content, and Atterberg limits), as well as the coefficient of erodibility and critical erosive shear stress at different locations were also measured to examine the variation of soil erodibility of Hongshihe Landslide Dam along the run-out direction, depth, and the water-flow direction. The results show that the coefficient of erodibility increases significantly along the run-out direction but decreases slightly with depth and along the water-flow direction, whereas the changes in critical erosive shear stress are limited along the run-out direction, depth, and the water-flow direction.
Highlights
Recent extreme flood events suggest that the vulnerability of river basins has increased over the past years as a consequence of climate change and engineering projects
The compaction experiment was performed for three material samples of the model grain size distribution (MGSD)
It separates the structurebearing fractions that might be the effective grain size distribution related to the common criteria from the potentially mobile fractions which not contribute to the structure
Summary
Recent extreme flood events suggest that the vulnerability of river basins has increased over the past years as a consequence of climate change and engineering projects. One of the negative results is that any change of flow condition in the subground might trigger internal erosion processes. In case of unstable structure seepage force can displace the fines within the grain skeleton during groundwater flow. This process is called suffosion and characterizes the relocation. SCOUR AND EROSION and discharge of fine particles through the pore space. The supporting granular skeleton will not be changed. Proceeding suffosion and additional external mechanical influences may cause instabilities of the supporting granular structure and subsequently, other types deformation may occur
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