| Summary: | 碩士 === 國立臺北科技大學 === 資源工程研究所 === 105 === In recent years, the large-scale construction projects and environmental resources related issues had brought attentions and rapid development on hydrogeology and other academic field connected to it. Rock engineering, including large-scale underground laboratory, tunnel excavation and hydrogeological well site, requires a certain degree of understanding on hydrogeology and hydraulic parameters, in order to facilitate subsequent planning and related construction. However, the presence of discontinuities in rock mass generates heterogeneity and anisotropy in its engineering characteristics, increasing variation of hydraulic and conductivity parameters, resulting in difficulty for determining representative parameters. Investigation and characterization of hydrogeological parameters of fracture rock masses are crucial to underground water exploiting. Among which, defining the hydrogeological representative elementary volume of the site is one of the key items. How to evaluate the hydrogeological unit to the scale of the target rock engineering is an important issue in hydrogeological parameters characterization.
Based on previous research results, this thesis present an assessment process for representative elementary volume on hydraulic parameter characterization on account of a hydraulic parameter characterization model for fractured rock mass. Investigation and statistical test are applied to estimate the variation degrees of representative elementary volume in site and associated hydraulic conductivity in rock mass, which further determine the scale influence on each hydraulic characteristic parameters, the methodology of the establishment and extension of application is through by Heshe hydrogeological well site, and another tunnel case project in initiative in north Taiwan. The evaluation method of representative elementary volume in hydraulic characteristic establish by statistical error propagation theory to calculate the varying degrees between the characteristic parameters and hydraulic conductivity, and the empirical formula of different hydraulic conductivity is discussed to find the variation range and plotted out different scales in a result. In order to understand the behavior of hydraulic conductivity associated with representative elementary volume changes, this research applies groundwater modeling system to establish numerical model and analysis it. Firstly, the anisotropy is simulated with a single element, the error between the two elements is calculated by numerical solution and analytic solution. Then, convert the goal of simulation scale to in-situ cross-hole pumping test which in heshe well site. Secondly, parameter sensitivity analysis is carried out to understand the representative elementary volume and its related parameters. Scale variation is using for complete numerical simulation methodology parallel verification, and establish the accuracy and correctness of the model. The case study is aimed at extending the application of different representative elementary volumes on the volume of seepage flow caused by tunnel excavation, which extend the application of methodologies in a large number of site surveys and numerical models.
The results show that the representative elementary volume evaluation program can effectively describe the change of the hydraulic characteristic parameters and the hydraulic conductivity coefficient with the scale variation by the statistical error propagation accumulation theory, and verify the groundwater anisotropy by numerical simulation. The related parameter sensitivity analysis shows that the numerical solution and the analytical solution will produce a certain range of errors in the setting of the boundary condition. The determination of the error value can provide the numerical model to improve the accuracy and correctness of the subsequent research. The hydraulic characteristic parameters of representative elementary volumes are on different scales, which changed in the groundwater seepage caused by tunneling, that with a certain degree of influence of groundwater through the three-dimensional simulation. We provide a valuable technical reference from the conceptual model, narrative model, and hydraulics model all the way to numerical model, through the outcome of methodology in designing verification and applying in this study.
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