ABSTRACT:
The slope failure of debris flow fans is distinct from common rock and soil slope failures due to the unique geotechnical features of debris flow sediment. This type of failure was not comprehensively and systematically studied in the past. In our recent research, based on the unique characteristics of debris flow fans, the Spencer slicing method with varying side force inclination is used to search for the possible critical slip surface, and the seepage force acting on the slip surface is considered in the calculation. This is done using spreadsheet-automated constraint optimization. A practical subroutine is developed to interpret the stability of a slope with varying physical parameters along the slope depth by using Visual Basic Application embedded in Microsoft Excel. To simulate the observed behavior of the slope failure, a series of triaxial tests was conducted to seek the varying physical parameters of in-situ debris flow sediment. The results of calculation are then compared with the actual slip surface observed in the field experiment. Significant findings result, regarding the mechanism of slope failure in debris flow fans.
1 INTRODUCTION
Numerous active debris flows on different scales exist across the mountainous areas of southwestern China, forming debris flow fans, as a result of local intense tectonic movement, changing climate and topography. When these debris flow fans are chosen as construction sites for buildings and roads, they pose a danger if failure occurs owing to different triggering factors. Such slope failures are distinct from those common with rock and soil slopes in terms of their features of composition, physical properties and deposition constitution. This type of failure was originally defined as “gravel slope landslide” (Hu et al. 2002). However, it was not comprehensively and systematically studied in the past.
