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Reservoir Rim Slope Stability Due To Rainfall And Operation Of Susu Dam
[Full Text]
AUTHOR(S)
Jimjali Ahmed, Ahmad Fadhli Mamat, Mohd Raihan Taha, Mohd Syazwan Md Rahim, Mohd Anuri Ghazali
KEYWORDS
Landslide, Slope stability, Transient flow, Unsaturated soil, Rainfall-induced slides, Rapid drawdown, Hazard map.
ABSTRACT
Susu Dam, in Cameron Highlands, is one of the dams in Malaysia with major fluctuation during operation. Leryar Village, which is a settlement of about 400 aborigines, is located on the bank and a rim slope failure could be catastrophic to the community. As such, this study investigates the landslide hazards due to the fluctuation of the reservoir and intense rainfall by conducting soil investigation, hazard mapping and advanced laboratory tests. Tests were conducted to obtain the hydraulic and mechanical properties of the soil, in the saturated and unsaturated states, which are necessary to simulate rapid drawdown and rainfall-induced shallow slides. Results of the slope stability analyses using this method differ greatly from the methods normally used by practitioners. Conventional methods would conclude that the slopes are sufficiently stable with Factor of Safety (FOS) values of at least 1.47, while this method, which involves rigorous testing and numerical modeling, resulted in an FOS of as low as 0.37. This implies the need to conduct extensive soil tests and apply the latest theories in soil mechanics to obtain reliable FOS for shallow failures involving transient flow conditions, such as rapid drawdown and rainfall infiltration. Aerial hazard map, using a qualitative approach, also agrees well with the FOS of the specific slopes. This suggests that a qualitative method of estimating landslide hazard could be used as a precursor to the advanced laboratory testing and slope stability analysis, which is costly and time consuming.
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