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  • 1
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    Experimental study and numerical modeling of the thermo-hydro-mechanical processes in soil freezing with different frost penetration directions (2021)
    Springer Berlin Heidelberg
    Details
    Publication Date: 2023-11-16
    Description: This research work presents an experimental and numerical study of the coupled thermo-hydro-mechanical (THM) processes that occur during soil freezing. With focusing on the artificial ground freezing (AGF) technology, a new testing device is built, which considers a variety of AGF-related boundary conditions and different freezing directions. In the conducted experiments, a distinction is made between two thermal states: (1) The thermal transient state, which is associated with ice penetration, small deformations, and insignificant water suction. (2) The thermal (quasi-) steady state, which has a much longer duration and is associated with significant ice lens formation due to water suction. In the numerical modeling, a special focus is laid on the processes that occur during the thermal transient state. Besides, a demonstration of the micro-cryo-suction mechanism and its realization in the continuum model through a phenomenological retention-curve-like formulation is presented. This allows modeling the ice lens formation and the stiffness degradation observed in the experiments. Assuming a fully saturated soil as a biphasic porous material, a phase-change THM approach is applied in the numerical modeling. The governing equations are based on the continuum mechanical theory of porous media (TPM) extended by the phase-field modeling (PFM) approach. The model proceeds from a small-strain assumption, whereas the pore fluid can be found in liquid water or solid ice state with a unified kinematics treatment of both states. Comparisons with the experimental data demonstrate the ability and usefulness of the considered model in describing the freezing of saturated soils.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: RWTH Aachen (3131)
    Keywords: ddc:550.78 ; Experimental study ; Frost heave ; Ice lens formation ; Phase-field modeling ; Soil freezing ; Thermo-hydro-mechanical coupling
    Language: English
    Type: doc-type:article
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    CITATION GEO-LEO
  • 2
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    Smoothed global stress maps based on the World Stress Maps database release 2016 (2018)
    GFZ Data Services
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    Publication Date: 2020-02-12
    Description: Dataset
    Language: English
    Type: info:eu-repo/semantics/workingPaper
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  • 3
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    Modelled stress state in the Bavarian Molasse Basin with quantified uncertainties (2020)
    GFZ Data Services
    Details
    Publication Date: 2020-03-19
    Description: These data are supplementary material to Ziegler & Heidbach (2020) and present the results of a 3D geomechanical-numerical model of the stress state with quantified uncertainties. The average modelled stress state is provided for each of the six components of the full stress tensor. In addition, the associated standard deviation for each component is provided. The modelling approach uses a published lithological model and the used data is described in the publication Ziegler & Heidbach (2020). The reduced stress tensor is derived using the Tecplot Addon GeoStress (Stromeyer & Heidbach, 2017).The model results are provided in a comma-separated ascii file. Each line in the file represents one of the approx. 3 million finite elements that comprise the model.
    Language: English
    Type: info:eu-repo/semantics/workingPaper
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  • 4
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    Quantification and Reduction of Uncertainties in 3D Stress Models (2020)
    In:  Abstracts
    Details
    Publication Date: 2020-07-30
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 5
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    Matlab script Stress2Grid v1.1 (2019)
    GFZ Data Services
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    Publication Date: 2021-04-10
    Description: The distribution of data records for the maximum horizontal stress orientation S_Hmax in the Earth’s crust is sparse and very unequally. To analyse the stress pattern and its wavelength and to predict the mean S_Hmax orientation on regular grids, statistical interpolation as conducted e.g. by Coblentz and Richardson (1995), Müller et al. (2003), Heidbach and Höhne (2008), Heidbach et al. (2010) or Reiter et al. (2014) is necessary. Based on their work we wrote the Matlab® script Stress2Grid that provides several features to analyse the mean S_Hmax pattern. The script facilitates and speeds up this analysis and extends the functionality compared to the publications mentioned before. This script is the update of Stress2Grid v1.0 (Ziegler and Heidbach, 2017). It provides two different concepts to calculate the mean S_Hmax orientation on regular grids. The first is using a fixed search radius around the grid points and computes the mean S_Hmax orientation if sufficient data records are within the search radius. The larger the search radius the larger is the filtered wavelength of the stress pattern. The second approach is using variable search radii and determines the search radius for which the standard deviation of the mean S_Hmax orientation is below a given threshold. This approach delivers mean S_Hmax orientations with a user-defined degree of reliability. It resolves local stress perturbations and is not available in areas with conflicting information that result in a large standard deviation. Furthermore, the script can also estimate the deviation between plate motion direction and the mean S_Hmax orientation. The script is fully documented by the accompanying WSM Technical Report 19/02 (Ziegler and Heidbach, 2019) which includes a changelog in the beginning.
    Language: English
    Type: info:eu-repo/semantics/other
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  • 6
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    Manual of the Python Script Apple PY v1.3 (2020)
    GFZ German Research Centre for Geosciences
    In:  WSM Technical Report
    Details
    Publication Date: 2021-04-10
    Description: In geosciences the discretization of complex 3D model volumes into finite elements can be a time-consuming task and often needs experience with a professional software. In particular, low angle outcropping or out-pinching geological units, i.e. geological layers that are represented in the model volume, pose serious challenges. Another example are changes in the geometry of a model, which can occur at one point of a project, when re-meshing is not an option anymore or would involve a significant amount of additional time to invest. In order to speed up and automate the process of discretization, Apple PY (Automatic Portioning Preventing Lengthy manual Element assignment for PYthon) separates the process of mesh-generation and unit assignment. It requires an existing mesh together with separate information on the depths of the interfaces between geological units (herein called horizons). These two pieces of information are combined and used to assign the individual elements to different units. The uniform mesh is created with a standard meshing software and has to be available as an Abaqus input file. The information on the horizons depths and lateral variations in the depths is provided in a text file. Apple PY compares the element location and depth with that of the horizons in order to assign each element to a corresponding geological unit below or above a certain horizon. The script files are provided for download at http://github.com/MorZieg/APPLE_PY. Table 0-1 gives an overview of the folder structure and input files with a short explanation.
    Language: English
    Type: info:eu-repo/semantics/report
    Format: application/pdf
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  • 7
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    Manual of the Python Script PyFAST Calibration v1.0 (2021)
    GFZ German Research Centre for Geosciences
    In:  WSM Technical Report
    Details
    Publication Date: 2021-04-27
    Description: The 3D geomechanical-numerical modelling of the in-situ stress state aims at a continuous description of the stress state in a subsurface volume. It requires observed stress information within the model volume that are used as a reference. Once the modelled stress state is in agreement with the observed reference stress data the model is assumed to provide the continuous stress state in its entire volume. The modelled stress state is fitted to the reference stress data records by adaptation of the displacement boundary conditions. This process is herein referred to as calibration. Depending on the amount of available stress data records and the complexity of the model the manual calibration is a lengthy process of trial-and-error modelling and analysis until best-fit boundary conditions are found. The Fast Automatic Stress Tensor Calibration (FAST Calibration) is a Python function that facilitates and speeds up this calibration process. By using a linear regression it requires only three model scenarios with different boundary conditions. The stress states from the three model scenarios at the locations of the reference stress data records are extracted. The differences between the modelled and observed stress states are used for a linear regression that allows to compute the displacement boundary conditions required for the best-fit modelled stress state. If more than one reference stress state is provided, the influence of the individual observed stress data records on the best-fit boundary conditions can be weighted. The script files are provided for download at: http://github.com/MorZieg/PyFAST_Calibration
    Language: English
    Type: info:eu-repo/semantics/report
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  • 8
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    Active faulting geometry and Stress pattern near complex strike-slip system along the Maghreb region: constraints on active convergence in the Western Mediterranean (2018)
    In:  Tectonics
    Details
    Publication Date: 2020-02-12
    Description: The Maghreb region (from Tunisia to Gibraltar) is a key area in the Western Mediterranean to study the active tectonics and stress pattern across the Africa‐Eurasia convergent plate boundary. In the present study, we compile comprehensive dataset of well‐constrained crustal stress indicators (from single focal mechanism solutions, formal inversion of focal mechanism solutions and young geologic fault slip data) based on our and published data analyses. Stress inversion of focal mechanisms reveal a first‐order transpression‐compatible stress field and a second‐order spatial variation of tectonic regime across the Maghreb region, with a relatively stable SHmax orientation from east to west. Therefore, the present‐day active contraction of the western Africa‐Eurasia plate boundary is accommodated by (1) E‐W strike‐slip faulting with reverse component along the Eastern Tell and Saharan‐Tunisian Atlas, (2) a predominantly NE‐trending thrust faulting with strike‐slip component in the Western Tell part, and (3) a conjugate strike‐slip faulting regime with normal component in the Alboran/Rif domain. This spatial variation of the present‐day stress field and faulting regime is relatively in agreement with the inferred stress information from neotectonic features. According to existing and newly proposed structural models, we highlight the role of main geometrically complex shear zones in the present‐day stress pattern of the Maghreb region. Then, different geometries of these major inherited strike‐slip faults and its related fractures (V‐shaped conjugate fractures, horsetail splays faults, imbricates fans, Riedel fractures) impose their component on the second‐ and third‐order stress regime. Neotectonic and smoothed present‐day stress map (mean SHmax orientation) reveal that plate boundary forces acting on the Africa‐Eurasia collisional plates control the long wavelength of the stress field pattern in the Maghreb. The current tectonic deformations and the upper crustal stress field in the study area are governed by the interplay of the oblique plate convergence (i.e., Africa‐Eurasia), lithosphere‐mantle interaction and preexisting tectonic weakness zones.
    Language: English
    Type: info:eu-repo/semantics/article
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  • 9
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    InProTunnel : Interfacial Processes between Mineral and Tool Surfaces - Causes, Problems and Solutions in Mechanical Tunnel Driving (2010)
    In:  GEOTECHNOLOGIEN Science Report
    Details
    Publication Date: 2020-02-12
    Description: During mechanical tunnel driving in fine grained soil or rock the excavated material often sticks to the cutting tools or conveying system, which may cause great difficulties in its excavation and transport. In the InProTunnel project this problem is faced on different scales particularly for the method of Earth Pressure Balanced (EPB) shield tunnelling. Major influences from tunnel boring machine (TBM) operation are identified by project data analyses, clogging propensity is evaluated by a new laboratory test, alternative manipulation techniques are developed based on modifications of the physico-chemical and electroosmotic behaviour of clay minerals and will be tested in an especially designed clogging test system.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 10
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    Matlab Script FAST Calibration v1.0 (2018)
    GFZ Data Services
    Details
    Publication Date: 2020-02-12
    Language: English
    Type: info:eu-repo/semantics/other
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