scholarly journals The SpannEnD project: 3-D stress prediction in the upper crust of Germany

2021 ◽  
Vol 1 ◽  
pp. 75-76
Author(s):  
Karsten Reiter ◽  
Steffen Ahlers ◽  
Sophia Morawietz ◽  
Luisa Röckel ◽  
Tobias Hergert ◽  
...  
Keyword(s):  
Stress State ◽  
Finite Elements ◽  
Boundary Conditions ◽  
Crustal Structure ◽  
Site Selection ◽  
Large Scale ◽  
Selection Process ◽  
Upper Crust ◽  
Initial And Boundary Conditions ◽  
Best Fit

Abstract. Assessment of the stability of deep geological repositories is a key task in the site selection process for high-level radioactive waste. Geomechanical stability is affected by endogenous and exogenous processes as well as by geotechnical operations. Stability prediction requires both an estimate of future stress changes as well as the initial, i.e. current stress state. However, data records on the current stress state in the upper crust are incomplete, sparse and spatially unevenly distributed. Therefore, geomechanical-numerical models are the only way to estimate the full stress tensor at locations where stress observations are not available. The main components of such a 3-D geomechanical model are the distribution of the elastic rock properties and rock density as well as stress data for the model calibration. The aim is to find the optimal initial and boundary conditions that result in a best-fit with respect to available stress data within the model volume. For this reason, the first open access database for stress magnitude data has been developed as an extension of the existing database on stress orientation data (world-stress-map.org). The new database contains 568 data records from Germany and surrounding areas, but only 15 % of these data records are of acceptable quality. Thus, only one reliable set of stress magnitude data is available for an area of 100×100 km2. Based on existing compilations of the crustal structure in and around Germany, data were merged into one model with the aim of estimating the 3-D stress state in Germany. Geomechanical models for stress estimation in Germany were created with varying geometrical and mechanical resolution. While the first model consists of four mechanical units and 1.3 million finite elements, the subsequent model consists of 12 units and 3.6 million finite elements. The results of the best-fit model with respect to the stress data reveal that there are regional differences when calculating the fracture potential, i.e. the distance to failure of intact rock as well as different values of slip tendency, which provides a measure of the reactivation potential of pre-existing faults. The observed variability of the modelled stress field can be used as a first-order assessment. Since model uncertainties are still high, the absolute values are not yet reliable. However, the model can be used to derive consistent initial and boundary conditions for models on a regional scale. Furthermore, it makes it possible to investigate the influence of the large-scale crustal structure on the overall stress pattern. The modelling workflow is set-up in a way that new information and higher resolution if needed can be implemented when more data are provided. This will improve the reliability of both, the model prediction on the large scale as well as the initial and boundary conditions for high-resolution regional models for selected areas during the site selection process.

scholarly journals An Open-Access Stress Magnitude Database for Germany

2021 ◽  
Vol 1 ◽  
pp. 71-72
Author(s):  
Sophia Morawietz ◽  
Moritz Ziegler ◽  
Karsten Reiter ◽  
Keyword(s):  
Stress State ◽  
Stress Field ◽  
Site Selection ◽  
Selection Process ◽  
Numerical Models ◽  
Spatial Scales ◽  
Damage Zone ◽  
Hydraulic Permeability ◽  
Stress Regime ◽  
Migration Pathways

Abstract. The stress field in the Earth's crust plays a central role in the site-selection process for a deep geological repository for high-level nuclear waste. Site selection and construction planning must take into account several factors that are influenced by the stress state. These include the excavation damage zone, the hydraulic permeability of the host rock, the self-sealing capacity, the effects of seismic events and the possible reactivation of faults as migration pathways for fluids and radionuclides. Likewise, the initial stress state is of central importance for the long-term studies to prove site safety over 1 Ma. To obtain a continuous description of the current 3D stress state, 3D geomechanical numerical models are used. These models have to be calibrated with data on stress magnitudes to obtain robust predictions. One of the central goals of the SpannEnD project (Spannungsmodell Endlagerung Deutschland, http://www.spannend-projekt.de, last access: 31 October 2021) was to build the first comprehensive and publicly accessible stress magnitude database for Germany, including a quality ranking of the data compiled from different methods. This database is the logical extension of the database of the World Stress Map project, in which so far only information on stress orientations and the stress regime has been compiled systematically. We present this first compilation of stress magnitude data published and made available by Morawietz et al. (2020). The stress data density is generally low and heterogeneous, so that a model calibration at the scale of a site model is not possible. Therefore, the main objective of the SpannEnD project is to develop a 3D geomechanical numerical model for the whole of Germany. The resulting 3D stress field will provide the basis for regional and local models in a later phase of the site selection process. Details on this are presented in three complementary contributions in this symposium by Reiter et al., Röckel et al. and Ahlers et al. The new Geology Data Act (Geologie-Datengesetz) now allows access to considerably more data, which will be incorporated into an update of the database after assessment according to the defined quality criteria. This database extension will improve the reliability of the predictions of the geomechanical models on different spatial scales.

scholarly journals 3-D geomechanical–numerical model of the contemporary crustal stress state in the Alberta Basin (Canada)

Solid Earth ◽  
2014 ◽  
Vol 5 (2) ◽  
pp. 1123-1149 ◽  
Author(s):  
K. Reiter ◽  
O. Heidbach
Keyword(s):  
Stress State ◽  
Numerical Model ◽  
Large Scale ◽  
In Situ Stress ◽  
Data Types ◽  
Stress Orientation ◽  
Stress Orientations ◽  
Alberta Basin ◽  
Best Fit

Abstract. In the context of examining the potential usage of safe and sustainable geothermal energy in the Alberta Basin, whether in deep sediments or crystalline rock, the understanding of the in situ stress state is crucial. It is a key challenge to estimate the 3-D stress state at an arbitrarily chosen point in the crust, based on sparsely distributed in situ stress data. To address this challenge, we present a large-scale 3-D geomechanical–numerical model (700 km × 1200 km × 80 km) from a large portion of the Alberta Basin, to provide a 3-D continuous quantification of the contemporary stress orientations and stress magnitudes. To calibrate the model, we use a large database of in situ stress orientation (321 SHmax) as well as stress magnitude data (981 SV, 1720 Shmin and 2 (+11) SHmax) from the Alberta Basin. To find the best-fit model, we vary the material properties and primarily the displacement boundary conditions of the model. This study focusses in detail on the statistical calibration procedure, because of the large amount of available data, the diversity of data types, and the importance of the order of data tests. The best-fit model provides the total 3-D stress tensor for nearly the whole Alberta Basin, and allows estimation of stress orientation and stress magnitudes in advance of any well. First-order implications for the well design and configuration of enhanced geothermal systems are revealed. Systematic deviations of the modelled stress from the in situ data are found for stress orientations in the Peace River and the Bow Island Arch as well as for leak-off test magnitudes.

scholarly journals 3-D-geomechanical-numerical model of the contemporary crustal stress state in the Alberta Basin

2014 ◽  
Vol 6 (2) ◽  
pp. 2423-2494 ◽  
Author(s):  
K. Reiter ◽  
O. Heidbach
Keyword(s):  
Stress State ◽  
Numerical Model ◽  
Large Scale ◽  
In Situ Stress ◽  
Data Types ◽  
Stress Orientation ◽  
Stress Orientations ◽  
Alberta Basin ◽  
Best Fit

Abstract. In the context of examining the potential usage of safe and sustainable geothermal energy in the Alberta Basin whether in deep sediments or crystalline rock, the understanding of the in-situ stress state is crucial. It is a key challenge to estimate the 3-D stress state at an arbitrary chosen point in the crust, based on sparsely distributed in-situ stress data. To address this challenge, we present a large-scale 3-D geomechanical-numerical model (700 km × 1200 km × 80 km) from a large portion of the Alberta Basin, to provide a 3-D continuous quantification of the contemporary stress orientations and stress magnitudes. To calibrate the model, we use a large database of in-situ stress orientation (321 SHmax) as well as stress magnitude data (981 SV, 1720 SHmin and 2 (+11) SHmax) from the Alberta Basin. To find the best-fit model we vary the material properties and primarily the kinematic boundary conditions of the model. This study focusses in detail on the statistical calibration procedure, because of the large amount of available data, the diversity of data types, and the importance of the order of data tests. The best-fit model provides the total 3-D stress tensor for nearly the whole Alberta Basin and allows estimation of stress orientation and stress magnitudes in advance of any well. First order implications for the well design and configuration of enhanced geothermal systems are revealed. Systematic deviations of the modelled stress from in-situ data are found for stress orientations in the Peace River- and the Bow Island Arch as well as for leak-off-test magnitudes.

DETERMINISTIC APPROACH TO WATERSHED MODELING

1971 ◽  
Vol 2 (3) ◽  
pp. 146-166 ◽  
Author(s):  
DAVID A. WOOLHISER
Keyword(s):  
Boundary Conditions ◽  
Watershed Modeling ◽  
Deterministic Approach ◽  
Mass Energy ◽  
Deterministic Models ◽  
Conservation Of Mass ◽  
Hydrologic Process ◽  
Theoretical Structure ◽  
Physically Based ◽  
Initial And Boundary Conditions

Physically-based, deterministic models, are considered in this paper. Physically-based, in that the models have a theoretical structure based primarily on the laws of conservation of mass, energy, or momentum; deterministic in the sense that when initial and boundary conditions and inputs are specified, the output is known with certainty. This type of model attempts to describe the structure of a particular hydrologic process and is therefore helpful in predicting what will happen when some change occurs in the system.

scholarly journals Experience of establishing and coordinating a nationwide network for bidirectional intussusception surveillance in India: lessons for multisite research studies

BMJ Open ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. e046827
Author(s):  
Manoja Kumar Das
Keyword(s):  
Quality Assurance ◽  
Site Selection ◽  
Information Seeking ◽  
Selection Process ◽  
Tertiary Care ◽  
Vaccine Safety ◽  
Secondary Outcome ◽  
Prospective Surveillance ◽  
Surveillance Network ◽  
Nationally Representative

ObjectivesTo document and share the process of establishing the nationally representative multisite surveillance network for intussusception in India, coordination, data management and lessons learnt from the implementation.DesignThis study combined both retrospective and prospective surveillance approaches.Setting19 tertiary care institutions were selected in India considering the geographic representation and public and private mixParticipantsAll children under-2 years of age with intussusceptionPrimary and secondary outcome measuresThe experience of site selection, regulatory approvals, data collection, quality assurance and network coordination were documented.ResultsThe site selection process involved systematic and objective four steps including shortlisting of potential institutions, information seeking and telephonic interaction, site visits and site selection using objective criteria. Out of over 400 hospitals screened across India, 40 potential institutions were shortlisted and information was sought by questionnaire and interaction with investigators. Out of these, 25 institutes were visited and 19 sites were finally selected to participate in the study. The multistep selection process allowed filtering and identification of sites with adequate capacity and motivated investigators. The retrospective surveillance documented 1588 cases (range: 14–652 cases/site) and prospective surveillance recruited 621 cases (range: 5–191 cases/site). The multilayer quality assurance measures monitored and ensured protocol adherence, complete record retrieval and data completeness. The key challenges experienced included time taken for obtaining regulatory and ethical approvals, which delayed completion of the study. Ten sites continued with another multisite vaccine safety surveillance study.ConclusionThe experience and results of this systematic and objective site selection method in India are promising. The systematic multistep site selection and data quality assurance methods presented here are feasible and practical. The lessons from the establishment and coordination of this surveillance network can be useful in planning, selecting the sites and conducting multisite and surveillance studies in India and developing countries.

Cyclic Breathing Simulations in Large Scale Models of the Lung Airway From the Oronasal Opening to the Terminal Bronchioles

2012 ◽  
Author(s):  
D. Keith Walters ◽  
Greg W. Burgreen ◽  
Robert L. Hester ◽  
David S. Thompson ◽  
David M. Lavallee ◽  
...  
Keyword(s):  
Steady State ◽  
Boundary Conditions ◽  
Large Scale ◽  
Whole Body ◽  
Patient Specific ◽  
Cfd Simulations ◽  
Reduced Order ◽  
Scale Models ◽  
Steady State Simulation ◽  
Conducting Zone

Computational fluid dynamics (CFD) simulations were performed for unsteady periodic breathing conditions, using large-scale models of the human lung airway. The computational domain included fully coupled representations of the orotracheal region and large conducting zone up to generation four (G4) obtained from patient-specific CT data, and the small conducting zone (to G16) obtained from a stochastically generated airway tree with statistically realistic geometrical characteristics. A reduced-order geometry was used, in which several airway branches in each generation were truncated, and only select flow paths were retained to G16. The inlet and outlet flow boundaries corresponded to the oronasal opening (superior), the inlet/outlet planes in terminal bronchioles (distal), and the unresolved airway boundaries arising from the truncation procedure (intermediate). The cyclic flow was specified according to the predicted ventilation patterns for a healthy adult male at three different activity levels, supplied by the whole-body modeling software HumMod. The CFD simulations were performed using Ansys FLUENT. The mass flow distribution at the distal boundaries was prescribed using a previously documented methodology, in which the percentage of the total flow for each boundary was first determined from a steady-state simulation with an applied flow rate equal to the average during the inhalation phase of the breathing cycle. The distal pressure boundary conditions for the steady-state simulation were set using a stochastic coupling procedure to ensure physiologically realistic flow conditions. The results show that: 1) physiologically realistic flow is obtained in the model, in terms of cyclic mass conservation and approximately uniform pressure distribution in the distal airways; 2) the predicted alveolar pressure is in good agreement with previously documented values; and 3) the use of reduced-order geometry modeling allows accurate and efficient simulation of large-scale breathing lung flow, provided care is taken to use a physiologically realistic geometry and to properly address the unsteady boundary conditions.

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