Search

iThis is an open access book. In view of growing conflicts over strategic georesources, the use of the geological subsurface in the sense of a regional resource is becoming increasingly important. In this context, georeservoirs are playing an important role for the energy transition not only as a source of energy but also as a storage facility and deep geological disposal for energy waste. The success of the energy transition also depends to a large extent on the efficient and safe use of underground resources.This book complements the previous basic book (GeomInt—Integrity of Host Rocks) with a series of application examples in different rock formations, clay, salt, and crystalline. The methodology developed in GeomInt is used, among others, in the Mont Terri underground research laboratory (Opalinus Clay), in the large borehole test in Springen (salt rock) and in the “Reiche Zeche” teaching and research mine (crystalline rock). In addition, new methodological developments are also taken up in experiments and models and embedded in workflows for geotechnical system analyses.The present book summarizes the results of the collaborative project “GeomInt2: Geomechanical integrity of host and barrier rocks - experiment, modeling and analysis of discontinuities” within the program: Geo Research for Sustainability (GEO: N) of the Federal Ministry of Education and Research (BMBF).

The principal interest of the GeomInt project consists of the investigation of effects on barrier integrity of three host rock formations: clay, salt and crystalline. The project focuses on distinct physical processes that can influence barrier integrity in these rocks, particularly those related to swelling and shrinkage, pressure-driven percolation and stress redistribution.

In this chapter we briefly describe information methods and technologies supporting geotechnical systems analyses of to large extend, i.e. using virtual reality methods for data and model integration (Sect. 5.1) and improving computational efficiency by using high-performance-computing techniques (Sect. 5.2).

iThis is an open access book. In view of growing conflicts over strategic georesources, the use of the geological subsurface in the sense of a regional resource is becoming increasingly important. In this context, georeservoirs are playing an important role for the energy transition not only as a source of energy but also as a storage facility and deep geological disposal for energy waste. The success of the energy transition also depends to a large extent on the efficient and safe use of underground resources.This book complements the previous basic book (GeomInt—Integrity of Host Rocks) with a series of application examples in different rock formations, clay, salt, and crystalline. The methodology developed in GeomInt is used, among others, in the Mont Terri underground research laboratory (Opalinus Clay), in the large borehole test in Springen (salt rock) and in the “Reiche Zeche” teaching and research mine (crystalline rock). In addition, new methodological developments are also taken up in experiments and models and embedded in workflows for geotechnical system analyses.The present book summarizes the results of the collaborative project “GeomInt2: Geomechanical integrity of host and barrier rocks - experiment, modeling and analysis of discontinuities” within the program: Geo Research for Sustainability (GEO: N) of the Federal Ministry of Education and Research (BMBF).

GeomInt2 is the follow-up project to the joint project “Geomechanical Integrity of Host and Barrier Rocks—Experiment, Modelling and Analysis of Discontinuities (GeomInt)”. The results of GeomInt made essential contributions to the analysis of the origin and development of discontinuities in clay, salt and crystalline rocks. Discontinuities are considered in many forms, be it as volumetrically distributed damage macroscopically representing fissures in the rock microstructure, discontinuities that can form anew at phase interfaces as well as discrete cracks or fracture networks. The pathways created or extended by these discontinuities entail the risk of migration of fluid phases from deep to near-surface geological layers and must therefore be taken into account in geotechnical safety analyses.

Success of our ongoing energy transition largely depends on subsurface exploitation. The subsurface can act as a “battery” to store energy dense fluids such as hydrogen, or a “host” to sequester unwanted substances such as carbon dioxide or radioactive waste. On the other hand, these operations cause the subsurface pressure and/or temperature to change and induce various (or cyclical) loadings to the surrounding formations. Their operational safety crucially hinges upon the subsurface integrity. The most imminent risk is nucleation of cracks that can lead to loss of mechanical integrity. Unlike hydraulic fracturing in geoenergy applications where one deliberately initiates cracks at certain targets, we normally design a system to avoid fracturing. At the designing stage, we thus have no prior knowledge of crack initiation locations or propagation paths. And, the computational designing tools should be able to assess the fracturing risk without such prior knowledge. In this study, we compared three computational approaches that do not require prescribed crack geometries—the discrete element method, the lattice element method, and the variational phase-field approach—against percolation experiments on rock salt. The experimental results show different fracture propagation paths depending on the boundary loads. The fracture geometries were reasonably matched by all approaches despite some differences in path irregularities. While the variational phase-field approach predicts relatively regular fracture paths, the paths predicted by the discrete and the lattice element methods are more irregular. These irregularities may seem more comparable to intergrain failure in real rocks, but they are also necessary triggers for fracture initiation in the discrete and the lattice element methods. In contrast, the fracture initiation in the variational phase-field approach is a realization of the energy minimization in the system, and the grain level descriptions are absen