Experimental Interpretation of a Historical Landslide Dam Failure at Diexi Town in Maoxian County,Sichuan Province,China
The structures and particle compositions of landslide-formed barrier dams exhibit significant differences between the upstream and downstream parts.Although research was conducted extensively by scholars on breaching mechanisms of various landslide dam bodies,there was limitation in the selection of dam particle sequences,and the complexity of the structure of barrier dams made the natural breaching process fundamentally different from the breaching of artificial earth-rock dams.This paper selected the landslide-induced river blocking event in 1933 triggered by the Ms7.5 earthquake in Diexi Town,Mao County,Sichuan Province,China as a case study.Through fieldwork and in-situ physical modeling experiments,the failure process of landslide dams with different particle gradings under a quasi-inverse grading structure was examined.(1)The erosion process of in-situ barrier dams built with quasi-inverse grading structure went through five stages of seepage,scouring,lateral erosion,downcutting,and destruction.(2)As particle gradation was d50=30 mm,a lateral corrosion developing at breach manifested as a holistic shear faulting,causing a rapid increase but slow recession of breaching flow rate,with the erosion curve showing an overall gentle trend.(3)As d50 was 14.2 mm,the lateral corrosion at the breach shifted to a holistic gravitational collapse,with the erosion curve being relatively steep,and the breach flow exhibited a pattern of rapid rise and quick recession.The research provides reference for the mechanism research and prevention of landslide dam break.
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