| dc.description.abstract | Extreme weather has recently caused many disasters worldwide. In recent years, the condition about extreme rainfall by Typhoon has caused the loss of numerous human lives and properties in Taiwan. In fact, half of top ten record of rainfall has occurred in last ten years. In August 8, 2009, Taiwan suffered from serious floods during Typhoon Morakot. In this extreme rainfall event, Levees along the Laonong River basin between the confluences with Chokuo River and Ailiao River experienced catastrophic failure. Because the design of such levees does not consider the effects of extreme rainfall, failure had occurred with unexpected situations.
Our goal is to find the reliability index of the levee in this basin for assessing the stability of each levee. We considered the three possible major failure mechanisms (the slope sliding failure of the levee, and the sliding and overturning failures of the retaining wall) with the failure-triggering parameters (the water level, the scouring depth, and the in-situ angle of internal friction). After the database of the safety factor corresponding to each failure-triggering parameters has been generated, the safety factors can be obtained by Monte Carlo simulation under different situations. Finally, we can get the reliability index with mean value and variation by the results of MCS.
In Chiuliao 1st Levee, sliding failures of the retaining wall has largest probability, but we can’t ignore the probability of slope sliding failure due to its high variability. In Gueishan Levee, slope sliding failure has highest reliability index. In low water level difference, sliding failures of the retaining wall has lowest reliability index. In high water level difference, overturning has lower reliability index than sliding failures of the retaining wall.
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