| Summary: | 碩士 === 國立臺灣大學 === 土木工程學研究所 === 106 === This study participates the Slopeland Community Voluntary Disaster Prevention Project and provides the groundwater simulation for the stability analysis of slopelands as the main task. Owing to the insufficiency of the field geographical and hydrological data, the study proposes a methodology for parameterizing and analyzing the slopeland hydrologic processes with the field data of the geography, hydrology and soil. The study utilizes the couple model of the vertical two-dimensional various saturation model and the horizontal two-dimensional slopeland width function to simulate the three-dimensional groundwater.
The study area is defined with the concept of stream line and smoothed elevation. Furthermore, the study simplifies the influence of the lateral inflow of the slopeland unit by transforming the lateral flow to an area and equivalent slope width and fitting the slope width function. To simplified the parameterizing process of soil parameters, the study applies the single exponential decay model to illustrate the influences of the weathering soil and biological activities on the soil characteristics and the slopeland soil hydraulic parameters distribution. By analyzing the monitoring data of the groundwater and the slope displacement, the study estimates the groundwater is impacted by the sliding surface and the head erosion from the slope foot.
For applying the couple model, this study redistributes the duration of the rainfall intensity with certain ratio to obtain the rainfall data with higher temporal resolution. Besides, the SCS method is applied to estimate the rainfall loss of the surface interception unit and draining system and to calculate the effective precipitation for infiltration. The deep percolation distribution of the bedrock at the bottom boundary is estimated by the couple model of the Dupuit assumption and the Laplace Equation.
The steady state distribution of groundwater is estimated by the Duapuit assumption and steady state precipitation. In order to provide reasonable initial condition efficiently with reduced Spin-up problem caused by the physical assumption difference between the Richards'' Equaiton and Dupuit assumption, the study simulates the infiltration with the estimated steady state distribution of groundwater and precipitation. Afterward, the study simulates the recession until the distribution of groundwater approaches the steady state again and utilizes this distribution as the initial condition. According to results of the initial condition, the soil hydraulic parameters and boundary conditions are re-adjusted to obtain the new initial condition and utilized to simulate the distribution of groundwater in study area.
In the end, the rationality of the methodology can be described by comparing the results and historical groundwater data. Moreover, the study illustrates the method for calibrating the parameter and the assumption in the methodology with the sufficient data.
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