| Summary: | 碩士 === 國立交通大學 === 土木工程系所 === 96 === Due to high population density in narrow coastal plains and the resistance of the public arisen from the not-in-my-backyard (NIMBY) attitude, a large portion of landfills in Taiwan are located in mountainous area. Current regulations on landfills do not require slope stability analysis while designing these landfills. As a result, the potential risk of slope failure of these landfills is very high. Furthermore, although the interfacial shear strength between the waste and geosynthetics is very important to landfill slope stability, it has seldom been considered in the design. The objective of this study is to perform stability analyses on block failures through weak interface in the bottom lining system for typical landfills on slopes. Two-dimensional slope stability analyses were conducted with SLOPE/W 2004. Geometric parameters such as height, slope angle of the back, the slope angle of the waste body, the length of the base, the width of the berm, and also the interfacial friction angle were varied to investigate their effect on the factor of safety against slope failure. In addition, slope analyses are also performed for earthquake conditions.
The results of 2-D stability analyses show that the factor of safety increases with lower height of wastes, longer length of waste body, higher slope angle of the back of the excavation, steeper face slope of waste body and higher interfacial friction angle. On the other hand, the factor of safety is only hardly affected by the berm width. While the length of waste body is smaller than 60m, failure is dominated by the interface sliding. While the length of waste body is greater than 70m, failure is governed by the rotational sliding within the waste body.
According to analysis, the standard section of MSW Landfills on Slope ( δ = 15°、α = 60°、β = 45°、H = 10 m、L = 30 m、B1 = 3 m). When it concerned to interface slide, we can provide the following suggestions in order to offer references of design and analysis: (1) the interfacial friction angle (δ) more than 19° at least, (2) the height of the wastes must less than 15 m or the height of every layer not more than 8 m, (3) the length of the base (L) should more than 40 m, (4) the width of the berm (B1) should not less than 3 m, (5) slope angle of the back (α) should 30° ~ 45° or 60° ~ 75° (6) the waste should be filled to a slope angle between 30°~60°
When the effect of earthquakes is taken into account, the decrease of safety factor ranges from 36% to 59%, which corresponds to a increase of the required minimum interface angle against translation slope failure from 8 degrees to 12 degrees. According to the results of this study, it can be concluded that the interfacial friction angle between the materials of the lining system should be carefully determined and stability analysis must be performed when designing the landfills on slopes. Furthermore, it is suggested that the minimum friction angle of the interfaces must be larger than 20 degrees to prevent translational slope failures.
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