Gelsenkirchen, Germany
Gelsenkirchen, Germany

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Altmann J.B.,Helmholtz Center Potsdam | Muller T.M.,CSIRO | Heidbach O.,Helmholtz Center Potsdam | Tingay M.R.P.,University of Adelaide | Weisshardt A.,ITASCA Consultants GmbH
Geothermics | Year: 2014

The spatio-temporal changes of the stress state in a geothermal reservoir are of key importance for the understanding of induced seismicity and planning of injection and depletion strategies. In particular the poro-elastic effects on the stress state due to re-injection or depletion of water are of interest for both geothermal projects and hydrocarbon exploitation. In addition to the conventionally used effective stress concept, poro-elasticity affects the stress tensor components differently as a function of changes in pore pressure. Here, we provide an analytical base for the long-term changes of the 3D stress tensor components as a function of pore pressure changes. Results indicate that for a constant rate of injection or depletion the coupling between pore pressure and all stress tensor components depends on the location in the reservoir with respect to the re-injection/depletion point as well as the time since the beginning of pore pressure changes. Our systematic analysis suggests that poro-elastic stress changes can even locally modify the given tectonic stress regime. Furthermore, the results predict that localized changes of maximum shear stress can lead to different fracture orientations than those expected when poro-elastic effects are not considered. These results indicate a need for 3D geomechanical-numerical studies of more realistic reservoir settings in order to study the 3D effects of pore pressure/stress coupling. Our generic 3D geomechanical-numerical study shows that less than two years of production of a single well changes shear stresses by 0.2. MPa. Thus, in reservoirs with decades of production shear stress change can reach sufficiently high values to re-activate pre-existing faults or even generate new fractures with unexpected orientations. © 2014 Elsevier Ltd.


Grant
Agency: European Commission | Branch: FP7 | Program: MC-ITN | Phase: FP7-PEOPLE-ITN-2008 | Award Amount: 3.24M | Year: 2009

The overarching aim of the PARDEM project is to provide high quality training to a group of young researchers to work within and to further develop the multidisciplinary field of DEM computational simulation of granular processes. Granular materials are estimated to constitute over 75% of all raw material feedstock to industry. They also present many challenges for innovation and fundamental science to solve problems in areas as diverse as natural disasters and industrial material handling which incur extensive economic losses. The Discrete Element Method (DEM) is a promising supradisciplinary facility providing both visual and quantitative details of the dynamics of particle assemblies. Although the method is established in academia, immature quantitative prediction capabilities and lack of DEM experts due to its rapid development hinder its use as an industrial engineering tool in Europe. To overcome this state a consortium of 6 industry and 5 academic partners is formed which engages the three key stakeholder groups (industrial users, DEM software developers and universities), vital for transforming DEM from a largely scientific tool into a widely adopted industrial tool and delivering increased competitiveness to the EU economy with significantly reduced development times of more efficient processes. The programme will provide for each fellow: a) in-depth training by research at the host site and on industrial secondments; b) sound multidisciplinary and intersectoral scientific training and understanding of industrial environments via courses and secondments; c) a programme of complementary skills training and network events to develop the researchers competencies and career options. The resulting new generation of DEM experts will speak a common language avoiding costly misunderstandings in commercial interactions of the three groups and drive the DEM technology to a level which will change the way equipment and granular processes are designed in EUROPE.


Grant
Agency: European Commission | Branch: FP7 | Program: MC-ITN | Phase: FP7-PEOPLE-2011-ITN | Award Amount: 4.32M | Year: 2012

Landslides and debris flows are serious geo-hazards common to countries with mountainous terrains. The high speed and the enormity of debris mass make debris flows one of the most dangerous natural hazards. Debris flows are often triggered by landslides partially or completely mobilizing into debris flows. Globally, landslides cause billions of dollars in damage and thousands of deaths and injuries each year. The numerous devastating events worldwide have made us aware of the complexity of landslides and debris flows and our insufficient knowledge to make reliable predictions. Traditional tools for prediction and design are based on limit equilibrium analysis for landslides and shallow water model with Finite Difference solver for debris flows. Usually soil and debris are modelled as single phase materials with constant material properties. That the simple models are unable to account for the complex behaviour of landslides and debris flows, which can be best described as multiphase and multiscale, is well known to researchers and stakeholders. Obviously there is an urgent need for better understanding of the triggering mechanisms, for reliable prediction of runout dynamics, deposition pattern and impact forces and for rational design of stabilization and protection structures. The last decade saw rapid developments in advanced constitutive models, experimental techniques in laboratory and in-situ, mechanics of multiphase media, localized deformation analysis, Discrete Element Method (DEM), advanced Finite Element Method (FEM) and Computational Fluid Dynamics (CFD). Training in these subjects has been rather sporadic and scattered in various disciplines. By integrating these advances into a coherent research network we expect to achieve the breakthrough in the research on landslides and debris flows, i.e. a consistent physical model with robust numerical scheme to provide reliable prediction and rational design of protection measures for landslides and debris flows.


Jas H.,7asConsult BV | Stahl M.,Schussler Plan Ingenieurgesellschaft mbH | Te Kamp L.,ITASCA Consultants GmbH | Konietzky H.,TU Bergakademie Freiberg | Oliver T.,Tensar International
Geotechnical Engineering for Infrastructure and Development - Proceedings of the XVI European Conference on Soil Mechanics and Geotechnical Engineering, ECSMGE 2015 | Year: 2015

This paper presents a procedure to simulate and analyse the behaviour of a geogrid embedded between a weak sub-grade and granular material and loaded with a passing wheel-load using PFC3D based on the specifications and under special consideration of the grain-size distribution, initial relative density, normal stress state as well as sample installation. The aim of this simulation is to learn how triaxial geogrids behave and what parameters are imperative for their fitness for use. Apart from the actual movements of the granular particles, model analysis of the geogrid behaviour and load dissipation is presented to understand the critical characteristics of triaxial geogrids. © The authors and ICE Publishing: All rights reserved, 2015.


Jas H.,7asConsult BV | Stahl M.,Schussler Plan Ingenieurgesellschaft mbH | Te Kamp L.,ITASCA Consultants GmbH | Konietzky H.,TU Bergakademie Freiberg | Oliver T.,Tensar International
Geotechnical Engineering for Infrastructure and Development - Proceedings of the XVI European Conference on Soil Mechanics and Geotechnical Engineering, ECSMGE 2015 | Year: 2015

The paper describes how numerical and tests have been conducted to reproduce the behaviour of geogrids embedded in granular material under special consideration of the grain-size, relative density, normal stress and installation. Granular soils and geogrids are simulated depending on a specific particle and parallel bond model and calibrated to the results of laboratory tests. An analysis is given of the actual deformations and stresses within the granular material during and after the loading The above knowledge and experience has been used to simulate a wheel passing over a stabilised sub-base on a weak sub-grade. The ultimate aim of this research is to learn how geogrids behave and what parameters are imperative for their fitness for use. © The authors and ICE Publishing: All rights reserved, 2015.


Grant
Agency: European Commission | Branch: FP7 | Program: MC-IAPP | Phase: FP7-PEOPLE-2012-IAPP | Award Amount: 801.97K | Year: 2013

Vegetation acts as a reinforcement for slopes due to the penetration of roots into the ground. Roots penetration is a time dependent phenomenon that is strongly connected to the hydrogeological condition of the slope and that interacts with soil properties. Roots reinforcement of soil is well documented and numerous formulae exist in literature. The reinforcement action is provided by roots penetrating below a potential slip surface and stiffening the slope. Roots contribution to stability depends both on roots tensile strength and on roots pull-out resistance. Both aspects have already been investigated and some models and formulae already exist which enable a qualitative evaluation of such contribution. Anyway no sophisticated software exists for the prediction of the three-dimensional numerical analysis of slope stabilized with vegetation. Existing software provides simple limit equilibrium analyses and is limited to plane problems. This research project joins together scientific expertise and numerical know-how to implement latestadvances in slope reinforcement with vegetation into commercial software. The resulting software will enable three-dimensional reinforced slope modeling. It will provide realistic soil-root interaction and root constitutive models. It will take into account roots growth with time and it will consider variations of the watertable and unsaturated conditions.


Graf F.,WSL Institute for Snow and Avalanche Research SLF | te Kamp L.,ITASCA Consultants GmbH | Auer M.,J. Krismer Handels GmbH | Acharya M.S.,University of Vienna | Wu W.,University of Vienna
Springer Series in Geomechanics and Geoengineering | Year: 2015

Stabilisation effects of plants are developing as a function of time. Within this scope, soil aggregation processes play a decisive role in reestablishing a protective vegetation cover. From this perspective we compared bare and vegetated soil, on the one hand artificially prepared and, on the other hand, derived from a recently landslide affected slope and an adjacent gully with 25 year old eco-engineering measures, respectively.In both cases, the planted specimens had a significantly higher soil aggregate stability compared to their respective control samples, with the relative increase from control to planted equal for both the natural and artificial samples.Aspects of the development and succession processes of plants are compared as well as rooting and the degree of mycorrhization. Additionally, soil development and the methodical approach are discussed as well as a new approach to modelling soil aggregate stability in respect of eco-engineering measures for slope stabilisation presented. © Springer International Publishing Switzerland 2015.


Krajewski W.,FH Darmstadt | Reul O.,FH Darmstadt | Te Kamp L.,ITASCA Consultants GmbH
Numerical Methods in Geotechnical Engineering - Proceedings of the 7th European Conference on Numerical Methods in Geotechnical Engineering | Year: 2010

Two case histories of sealings of structures subjected to seismic loads are presented. The first case history deals with the base sealing of a landfill, which has been stressed dynamically during the construction of a drainage gallery. The proof procedure showing that the excavation blastings have been acceptable for the sealing is discussed. In the second case history, a pit for blast impacts will be sealed at the base by a plastic liner and a concrete raft to protect the groundwater. Extended investigations comprising large scale blasting tests and dynamic finite element and finite difference analysis, respectively, have been performed to investigate the influence of the blast impacts on the sealing. In summary, the case history shows, that numerical analyses are well suited for the investigation of seismic problems. However, the required scientific and technical knowledge as well as the expenditure for system modelling and calibration are rather high. © 2010 Taylor & Francis Group, London.


Acharya M.S.,University of Vienna | Wu W.,University of Vienna | Auer M.,J. Krismer Handels GmbH | te Kamp L.,ITASCA Consultants GmbH
Springer Series in Geomechanics and Geoengineering | Year: 2015

Centrifuge testing is particularly suitable to model geotechnical processes and events because the increase in centrifugal force creates stresses in the model that are equivalent to gravitational force acting on the much larger prototype. The mechanisms of failure and the stresses observed in the model tests are generally the realistic representation of the actual ground movements and accumulation of stresses on prototype. Crib retaining walls made of different materials are used as special form of gravity walls in stabilizing slopes. The centrifuge test results of a model crib retaining wall made of mini bamboo sticks are reported in this paper. The centrifuge model test results are similar to the field test results of concrete crib walls. © Springer International Publishing Switzerland 2015.


Stahl M.,Am Muehlenhaus 1 | Konietzky H.,TU Bergakademie Freiberg | te Kamp L.,ITASCA Consultants GmbH | Jas H.,7asConsult BV
Acta Geotechnica | Year: 2013

A particle-based numerical simulation procedure is presented for the generation and calibration of geogrid-stabilised soil on the basis of experimental data. The paper describes how to simulate a biaxial geogrid depending on a specific particle and parallel bond model. Numerical and experimental pull-out tests have been performed to reproduce the pull-out force-strain behaviour of a biaxial geogrid specimen embedded in granular material under special consideration of the grain-size distribution, initial relative density, normal stress state as well as sample installation. Model analysis of soil mobilisation and geogrid deformation is presented to understand the significance of the interlocking effect as key mechanism for soil stabilisation. The procedure can be used for further investigations of the influence and effects of soil stabilisation depending on the significant properties of the interacting components (soils and geogrids). © 2013 Springer-Verlag Berlin Heidelberg.

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