Modellierung des Kluftgesteins als geologische Barriere fuer Deponien

Abstract

A special approach for numerical modeling of contaminant transport in fractured rock, as a natural migration barrier for waste respositories, is presented. The rock matrix and the fractures are simulated with specific transport formations and coupled in a single modell. The capacity of the rock matrix to accumulate contaminants is taken into consideration by a discrete simulation of matrix diffusion. Thus, the natural process of retardation due to matrix diffusion can be better simulated as by a standard introduction of an empirical parameter into the transport equation. The thesis consists of two parts. The first summarizes the basic processes of groundwater flow and transport. It addresses geogenic and antropogenic substances and their origin. Different transport phenomena and their mathematical formulations are derived. In the second part, a so called 'brush model' for groundwater simulation in fractured rock is developed. The 'brush handle' is discretized by 2D finite elements. Advective-dispersive transport with groundwater flow in the fracture is considered. In this 'britles of the brush' the contaminant diffuses into 1D finite elements perpendicular to the fractures. The approach is calibrated with results from forced gradient multi-tracer tests in the fractured claystone of the former toxic waste disposal site, Muenchehagen. In addition results of diffusion laboratory experiments are considered. The model validation was performed with an independent data set and a history-matching of the current situation at the site was carried out. Two different predictive scenarios with several parameter variations are presented. The study leads to the conclusion that the effect of matrix diffusion is an important property of fractured mudstone. This has to be taken into account for assessing waste repository performance in addition to the hydraulic properties of the natural migration barrier. (orig.)Available from TIB Hannover: RO 2460(45)+a+b / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman