Laboratory Experiments on Landslide Dam Failure Due to Piping: An Evaluation of 2011 Typhoon-Induced Landslide and Lands
Laboratory experiments were carried out to study erosional processes of landslide dam failure due to piping phenomenon with an evaluation of landslides and landslide dam triggered by 2011 Typhoon in Nara and Wakayama Prefectures of western Japan. Landslid
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Abstract Laboratory experiments were carried out to study erosional processes of landslide dam failure due to piping phenomenon with an evaluation of landslides and landslide dam triggered by 2011 Typhoon in Nara and Wakayama Prefectures of western Japan. Landslide dam models were built in a flume box with flume bed slope of 5°. To initiate piping, cylindrical pipe was laid in the dam at different horizontal and vertical locations. Four erosional stages were observed from the experiments. They include: appearance of wet spot/pipe development, continuation, progression, and breach. Stability and longevity of landslide dams due to piping were analyzed by varying heights of dams (HD), downstream slope angles, and horizontal positions of pipe. Results obtained show that stability and longevity of landslide dams depend on downstream slope angle, height and size of dams, and the erosive forces acting on the dam material. Results obtained from petrologic analysis of rock samples from the landslide and landslide dam sites show that the geomaterial of the areas are grainsupported which could lead to initiation of internal erosion and pipe formation. Keywords Wet spot Weathering
Backward erosion
Suffusion
Piping
Breach
1 Introduction Landslides and landslide dams are common geoenvironmental disasters occurring in tectonically active mountain belts of the world. Landslides occur as a result of rapid down-slope movement of soil and rock material under gravitational influence, while A. C. Okeke F. Wang (&) T. Sonoyama Y. Mitani Department of Geoscience, Shimane University, Matsue, 690-8504, Shimane, Japan e-mail: [email protected]
F. Wang et al. (eds.), Progress of Geo-Disaster Mitigation Technology in Asia, Environmental Science and Engineering, DOI: 10.1007/978-3-642-29107-4_30, Ó Springer-Verlag Berlin Heidelberg 2013
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natural dams such as landslide dams and moraine dams are common in steep confined valleys of mountainous regions. Triggering factors of landslides and landslide dams have been recorded in many parts of the world. Among these factors, snowmelt and rainfall constitute 90 % of studied landslide dams while volcanism, earthquake, devegetation and others make up the remaining 10 %. Landslide dams unlike earth dams are made up of heterogeneous materials that are poorly sorted, unconsolidated or moderately consolidated lacking filter zones to control internal seepages and piping (Costa and Schuster 1988). Loss of cohesion, internal friction angle of hillslope materials, increase in hillslope angle and relief have been observed to be preparatory factors for slope and landslide dam failures. The above-mentioned factors may be enhanced by stress released along intrinsic zones of weakness, repeated earthquake shaking, rock mass shattering along tectonic fault zones and slope debuttressing following deglaciation or precursory landsliding (Korup and Tweed 2007). Landslide dams have been classified into six categories based on their relation with the valley
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