| Summary: | 碩士 === 國立成功大學 === 水利及海洋工程學系 === 102 === Study on Seepage Failure of Landslide-Dam
Chin-Min Chen
Chjeng-Lun Shieh
Department of Hydraulic and Ocean Engineering, NCKU
SUMMARY
Landslide dams may fail due to overtopping, progressive or sudden failure of seepage. The peak discharge of flood produced by sudden failure of seepage is higher than other types. For practical application, a rapid and efficient assessment method for failure type of landslide dam is needed. By review of previous study, we conclude the factors be considered for evaluation. First, factors of overtopping and seepage failure include (a)Discharge; (b)Material properties of landslide dam; (c)Geometry of landslide dam. Second, factors of progressive and sudden failure of seepage include The Critical Stable Seepage Slope.
To analyze and quantify the relation of each factor of different failure type of landslide dam, we carry out the 46 laboratory experiments. At first, discriminant function of overtopping and seepage failure is analyzed by experiment results. The correcting rate of discriminant function is 95.5%. Then, The Critical Stable Seepage Slope can evaluate seepage failure is progressive or sudden.The result have good agreement of 8 field site case.
The study quantify the effect of geometry and hydrology parameters, the stability and failure type can be evaluated by quick evaluation of landslide dam. It could be helpful for emergency action of countermeasure of landslide dam.
Key words: Landslide Dam, Failure Type, The Critical Stable Seepage Slope.
INTRODUCTION
Extreme earthquake and rainfall events may result in landslide dams. Landslide dams will block the river flow and form the lake. Landslide dams usually fail soon after the lake formation (Peng and Zhang, 2012), and cause downstream flooding. Failure type of landslide dam include overtopping, progressive and sudden failure of seepage. Although sudden failure of seepage is not common case, but the peak discharge is higher than other types.(Takahashi and Kuang, 1988; Awal et al., 2007).
The main objective of this study is to evaluate failure type of landslide dam quickly by a rapid and efficient assessment method. We conclude the factors be considered for evaluation in this study, then to quantify the effect of geometry and hydrology parameters by 46 laboratory experiment results.
Failure type of landslide dam can be evaluated after formation of landslide dam, it could be helpful for emergency action of countermeasure of landslide dam.
MATERIALS AND METHODS
By review of previous study, we conclude the factors be considered for evaluation. First, factors of overtopping and seepage failure include (a)Discharge; (b)Material properties of landslide dam; (c)Geometry of landslide dam. Second, factors of progressive and sudden failure of seepage include The Critical Stable Seepage Slope.
At first, discriminant function of overtopping and seepage failure is analyzed by 46 experiment results. The correcting rate of discriminant function is 95.5%. Then, The Critical Stable Seepage Slope can evaluate seepage failure is progressive or sudden.The result have good agreement of 8 field site case.
RESULTS AND DISCUSSION
In figure 1, X axis and Y axis are dimensionless parameters. Overtopping and seepage failure separated well by ( )( ), the factor was combined with discharge and landslide dam shape. Equation of discriminant function is , the correcting rate is 95.5%. And seepage failure can be evaluated by , when the factor increase gradually, progressive failure of seepage was transformd into sudden failure of seepage.
Figure 2 is a rapid assessment method of landslide dam failure type. Collect Geometry and Hydrology parameters of landslide dam, and calculate relevant factors as ( )( ), . Then the result of landslide dam failure type can be provided after formation of landslide dam.
CONCLUSION
The study quantify the effect of geometry and hydrology parameters in failure type by 46 laboratory experiments. And the discriminant function of overtopping and seepage failure is based on experiment result, the correcting rate is 95.5%. Then seepage failure is progressive or sudden can be evaluated by The Critical Stable Seepage Slope.
The failure type of landslide dam can be evaluated immediately by the rapid assesment method, then it could provide a plausible results after formation of landslide dam.
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