02_experiments.tex

\chapter{Experimental Platform}
\label{cha:exp}
\Authors{Amir Shoarian Sattari, Thomas Fr\"uhwirt, Ralf-Michael Günther, Jobst Ma{\ss}mann, Wolfgang Minkley, Dirk Naumann, Mathias Nest, Daniel P\"otschke, Matthias Ruf}
%\todo{Please insert authors}

In order to investigate the barrier rocks, such as saltstone, claystone and crystalline, response under the coupled thermo-hydro-mechanical (THM) processes, a series of laboratory and field tests in the scope of the GeomInt project are carried out. A graphical abstract of experimental activities is depicted in Figure \ref{fig:appraoch}.

Initially, an introduction to the tested barrier rocks specifications and characteristics is provided (sec. \ref{sec:material-properties}). Next, the Opalinus Clay and saltstone responses under the coupled THM processes are investigated. Three-point bending, Brazilian disk and true triaxial tests are used to determine fracture toughness, splitting strength as well as changes of the mechanical and thermal properties under the coupled loadings, respectively. It is shown that the embedded layering orientation in the claystone samples has a significant effect on materials strength, deformation and frack paths (sec. \ref{sec:thm-lab-tests}).
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After determining the general material properties, distinct laboratory tests, which are chosen based on the unique purpose of the GeomInt project, are performed to analyze the shrinkage and swelling behavior of the claystone samples under free or in-situ loading conditions. The results again indicate the effect of the anisotropy on the swelling and shrinkage direction of the claystone material (sec. \ref{sec:lab-wp1}). 
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The fluid or gas driven percolation tests on Opalinus Clay and saltstone samples explore the change of the permeability, the required fracking pressure and the principle stress dependent frack paths. Additionally, the healing and frack closure characteristic of the barrier rocks are investigated. Moreover, the effect of the compressibility on the fluid flux and drop of the reservoirs pressure when using brine or gas as fracking medium is presented (sec. \ref{sec:lab-wp2}).
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The direct shear test on the crystalline gives an insight of the shear characteristics of the joints under the constant normal load (CNL) boundary condition. Additionally, the constant normal stiffness (CNS) test with the additional of extra load to the CNL procedure is performed. Specifically, for the crystalline samples, the diffusion and time-dependence states of the fractures under the cyclic loading conditions are characterized. Eventually, the flow and pressure dependency on the deformations of the frack volumes and paths are studied (sec. \ref{sec:lab-wp3}).
\index{Constant Normal Load (CNL) experiment}
\index{Constant Normal Stiffness (CNS) experiment}

\begin{figure}[!ht]
\centering
\includegraphics[width=0.95\textwidth]{figures/Amir_Experiment.png}
\caption{The conducted laboratory tests in the scope of GeomInt research project}
\label{fig:Amir_Experiment}
\end{figure} 
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\section{Rock Material Properties}
\label{sec:material-properties}
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\input{02_clay}
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\input{02_salt}
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\input{02_crystalline}
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\section{Thermo-Hydro-Mechanical Laboratory Tests}
\label{sec:thm-lab-tests}
In this section basic methods for rock characterization are briefly introduced such as 
characterization of rock structure (sec. \ref{subsec:structure}),
fracture toughness as materials resistance to fracture propagation (sec. \ref{sec:Fracture_Toughness_Exp}),
Brazilian tests to determine split tensile strength (sec. \ref{sec:Brazilian_Disk_Exp},
and triaxial tests to investigate the three-dimensional strain-strength behavior (sec. \ref{sec:True_Triaxial_Exp}).
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\input{0221_structure}
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\input{0222_thoughness}
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\input{0223_split}
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\input{0224_triax}
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\input{0225_triax}
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\section{Shrinkage and Swelling Laboratory Tests (WP1)}
\label{sec:lab-wp1}
\input{023_wp1}
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\section{Pressure Driven Percolation Laboratory Tests (WP2)}
\label{sec:lab-wp2}
\input{023_wp2}
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\section{Stress Redistribution Laboratory Tests (WP3)}
\label{sec:lab-wp3}
\input{023_wp3}
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