| Summary: | 碩士 === 國立中興大學 === 水土保持學系所 === 107 === In order to investigate the impact of subsurface drainage behavior of the drainage wells on the slopes stability and its stability mechanism. In this study, the three-dimensional numerical finite element method is used to simulate the drainage efficiency of the drainage wells in the large landslides and the mechanical mechanism of the drainage wells. The research is divided into two groups: The first one is to set up drainage wells in a large landslides to evaluation drainage benefit assessment.
For large landslides, according to the current collection of drilling data, topographic contour , geological maps, hydrogeological maps, soil/rock laboratory tests, grond movement and groundwater monitoring and other relevant information. It can be used to establish a 3-D numerical model of large landslides, and three models are built to explore four drainage wells. Subsequently, the #1, #2 drainage wells use the groundwater level monitoring value of the 2016 Meiji typhoon rainfall event as the storm water level, and the #3 and #4 drainage wells use the groundwater level monitoring value of the August 23, 2018 rainstorm event as the heavy rain. The water level, and the steady-state drainage analysis under normal and storm water levels, to explore the underground drainage capacity of the drainage wells, and the impact on the groundwater drawdown and slope stability. The potential sliding surface of the simulation results is roughly in agreement with with those from observation. At the same time, #3, #4 drainage wells the bottom horizontal drains regularly show a most efficient discharge rate, however the length of the horizontal drains of #1#,#2 drainage wells’ efficiency cannot be summarized . Due to the restrictions on land use, the drainage wells cannot be placed in the most appropriate position, but they still have the drainage effect they deserve. The new drainage wells flowmeter can be compared with the analog value in 2018.
In addition, the calculation of the deformations and failure behavior of the drainage wells shows that the drainage wells are deeper than the colluvium entering into sandstone layer, the deformations and compressive stress during drainage are much larger than those without crossing the sandstone, causing damage to the drainage wells . For the planning of the location of the later drainage wells, it is recommended to collect certain drilling datas first, or to design a bracket inside the wells body to provide sufficient pressure resistance
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