SFB1313, X: Discrete fracture models for flow, transport and deformation, and application to integrity studies of radioactive waste disposal sites

Forschungsprojekt im Rahmen des Sonderforschungsbereichs 1313 "Grenzflächengetriebene Mehrfeldprozesse in porösen Medien – Strömung, Transport und Deformation" gefördet durch Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 327154368

Projektbeschreibung (Englisch)

The development of numerical models for the simulation of flow and transport processes in fractured porous media is an active field of research, given the im- portance of fractures in a variety of geotechnical engineering applications such as groundwater management [10], geothermal energy [9] or unconventional gas production techniques [11]. Numerous approaches have been developed, which can generally be classified into continuum fracture models and discrete fracture-matrix (dfm) models. While in the first class of models the fractures are accounted for in an averaged sense, the fractures are explicitly captured in dfm models, and are often described by means of lower-dimensional geometries due to their small thicknesses.

In recent years, we have developed several dfm models for single-, two-phase, and non-isothermal flow, in which the fractures are described by means of lower- dimensional geometries, and where the flow along them is described on the basis of cross section-average partial differential equations. As a result, a mixed- dimensional system of equations describes describes flow through the fractured porous medium, with transmission conditions for the mass and energy transfer between the fractures and [3] the surrounding bulk medium. We have used sev- eral well-established finite-volume schemes for the spatial discretization of the resulting equations, and have studied and compared them in terms of accuracy and computational efficiency by means of numerical analysis.

This project aims, on one hand, on the further analysis and improvement of the developed models, and on the other hand, on the application of the models to research questions related to integrity issues of underground repositories for radioactive waste. Fractures are introduced in the near vicinity of the reposito- ries upon their excavation, and the question is how the surrounding fractured rock responds to the pressure and temperature increase that is expected to hap- pen as a consequence of the radioactive decay of the waste.

As the host rock surrounding the material is deformable, a crucial phe- nomenon might be the dilation of fractures in response to the pressure increase, which could give rise to preferential flowpaths and a somewhat increased perme- ability. Recently, we have extended our models to account for the deformation of the porous medium, which is able to capture changes in fracture aperture as a response to changing boundary conditions. In the scope of this project, we would like to improve these models and use them for studying the effect of frac- ture dilation on the permeability of the rock surrounding potential radioactive waste storage sites.

Leiter

Prof. Dr.-Ing. Rainer Helmig
apl. Prof. Dr.rer.nat Bernd Flemisch

Bearbeiter

Dr.-Ing. Dennis Gläser

Abteilung

LH2

Zeitraum

07/2020 - 06/2021

Finanzierung

Kontakt

Dieses Bild zeigt  Rainer Helmig
Prof. Dr.-Ing.

Rainer Helmig

Leiter

Dieses Bild zeigt  Bernd Flemisch
apl. Prof. Dr. rer. nat.

Bernd Flemisch

Akademischer Oberrat

Dieses Bild zeigt  Dennis Gläser
Dr.-Ing.

Dennis Gläser

wissenschaftlicher Mitarbeiter

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