| Summary: | 博士 === 國立交通大學 === 土木工程系 === 89 === In this study an accurate and efficient landsubsidence model due to groundwater overpumping which is a basic tool for application and management of groundwater resources has been developed and applied to practical case. First of all the analysis of order of magnitude for governing equations of three-dimensional coupled landsubsidence model shows that one-dimensional uncouple landsubsidence model is applicable when the flow pattern of groundwater is approximately horizontal or vertical. Based on the results, the concept of one-dimensional uncoupled model for modeling regional landsubsidence is proposed. The local severe landsubsidence can be zoomed and solved with a combination of three-dimensional coupled model.
In the one-dimensional uncoupled landsubsidence model, the concept of layered three-dimensional groundwater flow simulation is proposed. The governing equation for every layer is vertically integrated with an assumption that the pore pressure in the vertical direction is assumed to satisfy quadratic polynomial function. At the interface between two layers the continuity of pore pressure and flux has to be satisfied. The layered three-dimensional flow concept is able to efficiently simulate the fully three-dimensional flow pattern and the quasi three-dimensional flow pattern in which the groundwater flow of the aquifers and aquitard are horizontal and vertical, respectively.
The proposed three-dimensional coupled landsubsidence model is developed by using the technique of vertical integration as well. The pore pressure and displacements in the horizontal and vertical directions for every layer are assumed to satisfy quadratic polynomial function. Like the one-dimensional uncoupled model, at the interface between two layers the continuity not only of pore pressure and flux but also of displacement and stress has to be satisfied. In addition, to avoid the computational instability due to the large differences of soil parameters, the governing equations are non-dimensionalized.
Both one-dimensional uncoupled and three-dimensional coupled models are developed by using finite analytic method which is locally analytic and unconditionally stable and can deal with irregular boundary problems with the Cartesian coordinate system. After the two models are verified, they are applied to Tzuo-Suei River Basin for regional simulation and Kou-Hu for local modeling, respectively. The simulated results agree with the measured data quite well.
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