QUANTITATIVE ANALYSIS OF DYNAMIC FEATURES FOR ENTRAINMENT-OUTBURST INDUCED CATASTROPHIC DEBRIS FLOWS IN WENCHUAN EARTHQUAKE AREA
HUANG Xun1,2,3, TANG Chuan3
1. Chongqing Survey Institute, Chongqing 401121;
2. Chongqing Engineering Research Center of Geotechnical Engineering, Chongqing 401121;
3. State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu 610059
Many causative factors have changed acutely after the Wenchuan earthquake. They included the loose material, micro-topography and hydrological environment. Hence, the earthquake-induced debris flows are different from the general one. A whole debris flow process mechanism is developed and analyzed quantitatively using initiation discrimination model, bed-matrix erosion model and outburst-discharge enlargement model. It includes the initiation, transition and deposition phases. Moreover, the failure mechanism of the erosion-outburst-induced debris flow is illustrated clearly with an example. The result indicates that bed-matrix entrainment mechanism is the comprehensive outcome of the stress enlargement, strength degradation and material basis. The landslide dam outburst-induced discharge enlargement and the above-mentioned erosion mechanism are contributed to the large-scale debris flow. The case study of Hongchun catchment indicates that debris-flow discharge increases to 800.80m3·s-1 due to H02-03 landslide-dam outburst, and the entrainment-induced solid materials are half of the total magnitude, about 34.72×104m3.