Effect of Water Level Variation in River Channel on Slope Stability of Embankment

• Main Authors: Chiang, Hsiao-Cheng, 江效丞
• Other Authors: Shan, Hsin-Yu
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/84380176716244430562

碩士 === 國立交通大學 === 土木工程學系 === 100 === In the early years, many of revetments are built by using reinforcement concrete due to considering on the safety. But it is seldom been considering the impact of nature and the change of ecology after building in this type. According to the international attention degree on ecology is getting higher and higher in the recent years, the concept of ecological engineering which can get a balance with ecology becomes a popular method. Due to this conception, the materials of construction are using natural and porous materials rather than rigid materials. The concept of ecological engineering also affects the engineering in Taiwan. But many failure cases of revetments occur when encounter typhoons or rainstorm. However, So far, many studies of the revetment failure are focus on structure stability itself due to structural failure. Seldom of studies is focus on the effect of water level variation in river channel on slope stability of embankment. Therefore, the objects of study are concrete, dry stone masonry and concrete-masonry revetment. In this study is assuming that the revetment itself is strong enough without any breakdown and considering the effect of unsaturated zone, then studying in the effect of water level variation in river channel on slope stability of embankment by combining with different types of backfill, water level variation and time base of water level variation. The Procedure in this study at first step is simulating the seepage of water level variation in transient by using numerical simulation model－FEMWATER, then input the analysis result data from first step per time step in the slope stability model－Slope/W. After doing slope stability analysis, then can get the relationship between the factors of safety of embankment with time. Through this relationship clarify whether the failure of revetment is cause   by water level variation in river channel or not. The result of analysis reveals that the factor of safety is dominated by water pressure outside the slope during the full water level fluctuation. Because of the water level difference between the slope inside and outside, it cause a water force inward to the slope. The factors of safety of three types of revetment all alter with the water level fluctuation outside the slope. According to this result, it can say that the water level outside the slope affects huge than the change of the strength of backfill. On the other hand, the factor of safety is dominated by water pressure inside the slope during the rapid drawdown. Because of the water level difference between the slope inside and outside, it cause a water force outward to the slope. The factors of safety of three types of revetment are all decreasing with the rapid drawdown outside the slope. During the rapid drawdown, the degree of decreasing in factors of safety of concrete and concrete-masonry revetment is huge than the dry stone masonry revetment. From the variation of the factor of safety, three types of revetment are safe during the full water level fluctuation, but during rapid drawdown, only the dry stone masonry is safe, others are unsafe. But the probability of occurrence in which must be noted that due to the impact of extreme climate in recent years, the length of time to keep water in high level during full water level fluctuation lead to be rapid drawdown cannot be ignored.