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Olaf Kolditz - One of the best experts on this subject based on the ideXlab platform.
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simulation of heat extraction from crystalline rocks the influence of coupled processes on differential reservoir cooling
Geothermics, 2006Co-Authors: Christopher Mcdermott, Helmut Tenzer, Andreas R L Randriamanjatosoa, Olaf KolditzAbstract:Abstract Processes operating during the extraction of heat from fractured rocks influence dynamically their fluid flow and heat transport characteristics. The incorporation of pressure- and temperature-dependent rock parameters, coupled with Geomechanical deformation, is particularly important for predictive Modelling of geothermal reservoirs hosted in crystalline rock masses. Changes in flow and transport parameters of fractures caused by variations in local effective stress are computed using an experimentally validated Geomechanical Model [McDermott, C.I., Kolditz, O., 2006. Geomechanical Model for fracture deformation under hydraulic, mechanical and thermal loads. Hydrogeol. J. 14, 487–498]. Local effective stress changes are linked to alterations in reservoir fluid pressures, and to in situ stress conditions, including the build-up of thermal stresses resulting from the cooling of the rock mass. These processes are simulated using a finite-element Model in order to study the behaviour of the Spa Urach (southwestern Germany) potential geothermal reservoir. The Model couples mechanical deformation and alteration of fracture parameters with pressure-, temperature- and salinity-dependent fluid parameter functions. The effects of potential reservoir damage on reservoir productivity are investigated to help identify optimal heat recovery schemes for the long-term economical exploitation of geothermal systems. Simulation results indicate that preferential fluid flow paths and shortcuts may develop, depending on the mechanical and thermal stress releases that occur during intense exploitation of these systems.
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Geomechanical Model for fracture deformation under hydraulic, mechanical and thermal loads
Hydrogeology Journal, 2006Co-Authors: Chris Mcdermott, Olaf KolditzAbstract:Hydraulic flow and transport (heat and solute) within crystalline rocks is dominated by the fracture systems found within them. In situ stress conditions have a significant impact on the hydraulic, mechanical and thermal coupled processes, and quantification of these processes provides a key to understanding the often transient time-dependent behaviour of crystalline rocks. In this paper, a Geomechanical Model is presented which describes fracture closure as a function of effective stress and the changes in parameters such as storage, permeability, porosity and aperture. Allowing the fracture closure to be defined by the change in normal effective stress provides a link to the numerical consideration of parametrical changes due to rock stress alterations caused for example by changes in fracture fluid pressure, stress release, tectonic stress, thermal stress, orientation of the natural fracture in the pervasive stress system and local changes in a rock mass due to stress alteration. The Model uses geometrical considerations based on a fractal distribution of apertures on the fracture surface, and applies well-established analytical elastic deformation solutions to calculate the deformation response to changes in effective stress. Analysis of the fractal generation method allows a standard normal distribution of fracture apertures to be predicted for all common fractal dimensions relating to a 2D surface. Changes in the fracture aperture are related to hydraulic functions such as permeability, storage and porosity of the fracture. The Geomechanical Model is experimentally validated against laboratory scale experimental data gained from the closure of a fractured sample recovered at a depth of 3,800 m from the KTB pilot borehole. Parameters for matching the experimental data were established externally, the only fitting parameters applied were the minimum and maximum contact area between the surfaces and the number of allowable contacts. The Model provides an insight into the key processes determining the closure of a fracture, and can act as a material input function for numerical Models linking the effects of changes in the stress field, hydraulic or thermal conditions, to the flow and transport parameters of a fractured system. El flujo hidráulico y transporte (de calor y solutos) dentro de rocas cristalinas está dominado por los sistemas de fracturas que se encuentran en ellas. Las condiciones de esfuerzos in-situ tienen un impacto significativo en los procesos aparejados termales, mecánicos e hidráulicos y la cuantificación de estos procesos aporta una clave para entender el frecuente comportamiento transitorio dependiente de las rocas cristalinas. En este artículo se presenta un Modelo geomecánico que describe el cierre de fracturas en función del esfuerzo efectivo y los cambios en parámetros tal como almacenamiento, permeabilidad, porosidad y apertura. El definir el cierre de fractura mediante el cambio en esfuerzo normal efectivo aporta un vínculo con la consideración numérica de cambios paramétricos ocasionados por alteraciones de esfuerzos en la roca causadas, por ejemplo, por cambios en presión de fluidos en fractura, liberación de esfuerzo, esfuerzo tectónico, esfuerzo termal, orientación de fracturas naturales en el sistema de esfuerzos penetrante, y cambios locales en una masa rocosa ocasionados por alteración de esfuerzos. El Modelo utiliza consideraciones geométricas basadas en la distribución fractal de aperturas en la superficie de fractura y aplica soluciones analíticas bien establecidas de deformación elástica para calcular la respuesta de deformación a cambios en el esfuerzo efectivo. Los análisis del método de generación fractal permiten predecir una distribución normal standard para la distribución de aperturas de fracturas para todas las dimensiones fractales comunes que se relacionan con una superficie 2D. Los cambios en la apertura de fractura se relacionan con funciones hidráulicas tal como permeabilidad, almacenamiento y porosidad de la fractura. El Modelo geomecánico se ha validado experimentalmente en contra de datos experimentales a escala de laboratorio obtenidos a partir del cierre de una muestra fracturada recuperada a una profundidad de 3,800 m en el pozo piloto KTB. Se establecieron externamente parámetros que se ajustan a los datos experimentales, con los parámetros de ajuste aplicados que fueron el área máxima y mínima de contacto entre las superficies y el número de contactos permisibles. El Modelo arroja luz sobre los procesos clave que determinan el cierre de una fractura y puede actuar como un material de función de entrada para Modelos numéricos que vinculan los efectos de cambios en el campo de esfuerzos, condiciones termales o hidráulicas, con los parámetros de flujo y transporte de un sistema fracturado. L’écoulement et le transport (chaleur et soluté) dans les roches cristallines sont dominés par les systèmes de fracture. Les conditions de stress in-situ ont un impact significatif sur l’hydraulique, les processus couplés de mécanique et thermique et la quantification de ces processus apportent une clé pour comprendre le comportement transitoire des roches cristallines. Dans cet article un modèle géomécanique est présenté, modèle qui décrit la fermeture des fractures comme une fonction de la contrainte effective et des changements de paramètres tels le coefficient d’emmagasinement, la perméabilité, la porosité et l’ouverture. En s’accordant que la fermeture des fractures est définit par les changements de la contrainte effective normale, on apporte le lien avec la considération numérique des changements paramétriques dus aux altérations de la contrainte des roches, causés par exemple par des variations de la pression des fluides dans les fractures, du dégagement de la contrainte, des contraintes tectoniques et thermiques, des orientations des fractures naturelles dans le système de contraintes pénétrantes, et des changements locaux dans un massif de roches dus à l’altération des contraintes. Le modèle utilise des considérations géométriques basées sur une distribution fractale des ouvertures à la surface des fractures, et permet d’établir des solutions analytiques de la déformation élastique pour calculer la réponse de la déformation à la contrainte effective. L’analyse de la méthode par génération fractale permet de prédire une distribution normale standard de l’ouverture des fractures, pour toutes les dimensions fractales en relation avec les surfaces 2D. Les changements dans l’ouverture des fractures sont mis en relation avec les fonctions hydrauliques tels la perméabilité, l’emmagasinement et la porosité de la fracture. Le modèle géoméchanique est expérimentalement validé à l’échelle du laboratoire sur un échantillon fracturé récupéré à une profondeur de 3,800 mètres sur le puits du site pilote KTB. Les paramètres du calibrage des données expérimentales ont été établies extérieurement, les seuls paramètres utilisés étant les surfaces de contact minimum et maximum, et le nombre de contacts permis. Le modèle apporte une connaissance perspicace sur le processus clé déterminant la fermeture des fractures, et peut servir de fonction input dans les modèles numériques reliant les effets des variations de la contrainte du terrain, les conditions hydrauliques ou thermales, les paramètres de l’écoulement et du transport et les systèmes de fracture.
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Geomechanical Model for fracture deformation under hydraulic mechanical and thermal loads
Hydrogeology Journal, 2006Co-Authors: Christoper Mcdermott, Olaf KolditzAbstract:Hydraulic flow and transport (heat and solute) within crystalline rocks is dominated by the fracture systems found within them. In situ stress conditions have a significant impact on the hydraulic, mechanical and thermal coupled processes, and quantification of these processes provides a key to understanding the often transient time-dependent behaviour of crystalline rocks. In this paper, a Geomechanical Model is presented which describes fracture closure as a function of effective stress and the changes in parameters such as storage, permeability, porosity and aperture. Allowing the fracture closure to be defined by the change in normal effective stress provides a link to the numerical consideration of parametrical changes due to rock stress alterations caused for example by changes in fracture fluid pressure, stress release, tectonic stress, thermal stress, orientation of the natural fracture in the pervasive stress system and local changes in a rock mass due to stress alteration. The Model uses geometrical considerations based on a fractal distribution of apertures on the fracture surface, and applies well-established analytical elastic deformation solutions to calculate the deformation response to changes in effective stress. Analysis of the fractal generation method allows a standard normal distribution of fracture apertures to be predicted for all common fractal dimensions relating to a 2D surface. Changes in the fracture aperture are related to hydraulic functions such as permeability, storage and porosity of the fracture. The Geomechanical Model is experimentally validated against laboratory scale experimental data gained from the closure of a fractured sample recovered at a depth of 3,800 m from the KTB pilot borehole. Parameters for matching the experimental data were established externally, the only fitting parameters applied were the minimum and maximum contact area between the surfaces and the number of allowable contacts. The Model provides an insight into the key processes determining the closure of a fracture, and can act as a material input function for numerical Models linking the effects of changes in the stress field, hydraulic or thermal conditions, to the flow and transport parameters of a fractured system.
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investigation of coupled hydraulic Geomechanical processes at the ktb site pressure dependent characteristics of a long term pump test and elastic interpretation using a Geomechanical facies Model
Geofluids, 2006Co-Authors: Christopher Mcdermott, M Lodemann, I Ghergut, Helmut Tenzer, Martin Sauter, Olaf KolditzAbstract:The German Continental Deep Drilling Program comprising a pilot borehole down to 4000 m and a main borehole down to 9101 m in southeast Germany (KTB) is continuing to provide a unique opportunity for the identification of important factors and processes in deep-seated fluid and energy transfer. In situ stress conditions significantly impact flow, transport and exchange characteristics of fracture networks that dominate the permeability of crystalline reservoir rocks. In this paper, several scales of information are combined to present a fully three-dimensional hydraulic finite element Model of the principal KTB fault zones, and linked to a Geomechanical Model describing the alteration of the hydraulic parameters with stress changes caused by fluid extraction. The concept of Geomechanical facies is introduced to define and characterize architectural elements in the subsurface system. Evaluation of a long-term pump test in the KTB pilot hole, June 2002–July 2003, coupled with a Geomechanical Model gives an insight into some of the elastic and nonelastic processes controlling hydraulic transport in the basement rocks. Trends in the decline of the permeability and the degree of storage in the system could only partially be explained by elastic processes, clearly indicating the importance of nonelastic processes. A number of inelastic processes are suggested as areas for further research.
Oliver Heidbach - One of the best experts on this subject based on the ideXlab platform.
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forward Modelling of seismicity rate changes in georeservoirs with a hybrid Geomechanical statistical prototype Model
Geothermics, 2014Co-Authors: Amir Hakimhashemi, Oliver Heidbach, Martin Schoenball, Arno Zang, Gottfried GrunthalAbstract:Abstract A key challenge for the development of Enhanced Geothermal Systems (EGS) is to forecast the probability of occurrence of seismic events that have the potential to damage man-made structures. Induced seismicity results from man-made time-dependent stress changes, e.g., due to fluid injection, shut-in and fluid or steam production. To accomplish a classical Probabilistic Seismic Hazard Assessment (PSHA) a catalogue of induced seismicity is required. In addition, PSHA does not return any practical recommendation for how to treat the reservoir Geomechanically in order to lower the probability of occurrence of induced seismicity. Thus, we propose to link the simulated stress changes from forward Geomechanical numerical reservoir Models with the statistical rate-and-state approach of Dieterich (1994) . Using this link we translate the Modelled time-dependent stress changes into time-dependent changes of seismicity rates. This approach is general and independent of the incorporated Geomechanical numerical Model used. We exemplify our hybrid Model approach using a Geomechanical Model that describes the stimulation of the well GPK4 at the EGS site in Soultz-sous-Forets (France) including the shut-in phase. By changing the injection rate in the Geomechanical Model we generate various synthetic injection scenarios. With these scenarios we can study the effect on the seismicity rate and provide a recommendation for which injection experiment results in the least increase of seismicity rate. The results indicate an explicit coupling between the time-depending stress changes and the induced seismicity rate for each scenario. Even though the hybrid Model cannot be used in general to derive absolute values of the rate of induced seismicity a priori (this is only possible if the Geomechanical Model can be calibrated against observed induced events), it serves as a tool to test the effect of stress changes on the induced seismicity rate. The approach described here is a prototype Model illustrating the general workflow. In particular the Geomechanical Model can be replaced by any other type of reservoir description.
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Geomechanical Model of the marmara sea region i 3 d contemporary kinematics
Geophysical Journal International, 2011Co-Authors: Tobias Hergert, Oliver Heidbach, Anne Becel, Mireille LaigleAbstract:SUMMARY We investigate by means of a 3-D Geomechanical Model the relationship between structural elements and contemporary kinematics in the Marmara Sea region, northwest Turkey. The recently imaged fault system beneath the Marmara Sea is incorporated into the Model as frictional surfaces with varying strike and dip. The Main Marmara Fault is implemented as through-going and is accompanied by mostly non-vertical second-order faults. Topography, basement-topography and the Moho become mechanically effective through changes in density and elastic parameters across these horizons. The Model is subjected to gravity and kinematic boundary conditions. The ultimate goal of this study is to set up a 3-D Model that is consistent with both, kinematic observations and stress data. The stress results are presented in a complementary paper. In this paper we present the Modelled long-term 3-D kinematics in terms of fault slip rates, rotations, vertical motion and sense of fault slip. The Model results agree with Global Positioning System velocities, geological fault slip rates, palaeomagnetic measurements and with the observed pattern of subsidence and uplift. Furthermore, our tectonically driven vertical velocities can be linked to landscape and basin evolution and to features of sedimentation. Our results indicate that the Main Marmara Fault can be interpreted as a through-going fault that slips almost purely in a strike-slip sense. Nevertheless, and not contradictory to the previous statement, there is significant dip-slip motion at some sections of the Main Marmara Fault. The agreement of the Modelled 3-D kinematics with Model-independent observations supports that the main structural details of the fault system are accounted for. Sensitivity analysis of Model parameters reveals that changes in rock properties and the initial stress state have minor influence on the 3-D kinematics. We conclude that the 3-D structure of the fault system is the key control of the kinematics. The slip rate of the Main Marmara Fault from our Model is lower than previous estimates and shows high variability along strike (12.8–17.8 mm a–1). The latter indicates that stress accumulation is non-uniform along strike.
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Geomechanical Model of the marmara sea region ii 3 d contemporary background stress field
Geophysical Journal International, 2011Co-Authors: Tobias Hergert, Oliver HeidbachAbstract:SUMMARY We present the contemporary 3-D background stress field of the Marmara Sea region derived from a Geomechanical Model. The background stress field (i.e. the component of the absolute stress state that is time-independent over the seismic cycle) primarily depends on the distribution of density and elastic parameters, on the acting far-field stresses from plate boundary forces and on fault geometries. We take these into account to predict the 3-D background stress field including its spatial variations. Technically, our Model concept involves the definition of an appropriate initial stress state accounting for the gravitational reference stress state of the crust, which is then changed by plate tectonics until the 3-D background stress field has evolved. The Modelled stress field agrees well with observations from earthquake focal mechanism solutions and their formal stress inversion, with orientation of maximum horizontal stress and with the distribution of seismicity in the Marmara Sea. In particular in the vicinity of fault bends the stress field deviates considerably from the regional NW–SE oriented maximum horizontal stress and exhibits variability of the stress regime. Our Model results are consistent not only with dynamic observations but also with kinematic ones. Various kinematic observations are understandable from the stress field. We show that a stress regime that indicates normal faulting in the basins is nonetheless reconcilable with almost pure strike-slip motion on the Main Marmara Fault. The distribution of seismicity in the Marmara Sea can be explained in first order by the distribution of critical differential stress, which is closely related to local fault geometries. We refer the wide absence of seismicity between the bend of the Main Marmara Fault near Istanbul and the Central basin to the relatively plane fault geometry of that segment. Normal stress on the Main Marmara Fault is highly variable along strike, which makes segment-wise rupture more likely than a rupture of the seismic gap at once. Comparably low normal stress on the Prince's Islands Segment indicates a shorter interevent time for this fault segment than for the central segment of the Main Marmara Fault.
Tobias Hergert - One of the best experts on this subject based on the ideXlab platform.
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Geomechanical Model of the marmara sea region i 3 d contemporary kinematics
Geophysical Journal International, 2011Co-Authors: Tobias Hergert, Oliver Heidbach, Anne Becel, Mireille LaigleAbstract:SUMMARY We investigate by means of a 3-D Geomechanical Model the relationship between structural elements and contemporary kinematics in the Marmara Sea region, northwest Turkey. The recently imaged fault system beneath the Marmara Sea is incorporated into the Model as frictional surfaces with varying strike and dip. The Main Marmara Fault is implemented as through-going and is accompanied by mostly non-vertical second-order faults. Topography, basement-topography and the Moho become mechanically effective through changes in density and elastic parameters across these horizons. The Model is subjected to gravity and kinematic boundary conditions. The ultimate goal of this study is to set up a 3-D Model that is consistent with both, kinematic observations and stress data. The stress results are presented in a complementary paper. In this paper we present the Modelled long-term 3-D kinematics in terms of fault slip rates, rotations, vertical motion and sense of fault slip. The Model results agree with Global Positioning System velocities, geological fault slip rates, palaeomagnetic measurements and with the observed pattern of subsidence and uplift. Furthermore, our tectonically driven vertical velocities can be linked to landscape and basin evolution and to features of sedimentation. Our results indicate that the Main Marmara Fault can be interpreted as a through-going fault that slips almost purely in a strike-slip sense. Nevertheless, and not contradictory to the previous statement, there is significant dip-slip motion at some sections of the Main Marmara Fault. The agreement of the Modelled 3-D kinematics with Model-independent observations supports that the main structural details of the fault system are accounted for. Sensitivity analysis of Model parameters reveals that changes in rock properties and the initial stress state have minor influence on the 3-D kinematics. We conclude that the 3-D structure of the fault system is the key control of the kinematics. The slip rate of the Main Marmara Fault from our Model is lower than previous estimates and shows high variability along strike (12.8–17.8 mm a–1). The latter indicates that stress accumulation is non-uniform along strike.
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Geomechanical Model of the marmara sea region ii 3 d contemporary background stress field
Geophysical Journal International, 2011Co-Authors: Tobias Hergert, Oliver HeidbachAbstract:SUMMARY We present the contemporary 3-D background stress field of the Marmara Sea region derived from a Geomechanical Model. The background stress field (i.e. the component of the absolute stress state that is time-independent over the seismic cycle) primarily depends on the distribution of density and elastic parameters, on the acting far-field stresses from plate boundary forces and on fault geometries. We take these into account to predict the 3-D background stress field including its spatial variations. Technically, our Model concept involves the definition of an appropriate initial stress state accounting for the gravitational reference stress state of the crust, which is then changed by plate tectonics until the 3-D background stress field has evolved. The Modelled stress field agrees well with observations from earthquake focal mechanism solutions and their formal stress inversion, with orientation of maximum horizontal stress and with the distribution of seismicity in the Marmara Sea. In particular in the vicinity of fault bends the stress field deviates considerably from the regional NW–SE oriented maximum horizontal stress and exhibits variability of the stress regime. Our Model results are consistent not only with dynamic observations but also with kinematic ones. Various kinematic observations are understandable from the stress field. We show that a stress regime that indicates normal faulting in the basins is nonetheless reconcilable with almost pure strike-slip motion on the Main Marmara Fault. The distribution of seismicity in the Marmara Sea can be explained in first order by the distribution of critical differential stress, which is closely related to local fault geometries. We refer the wide absence of seismicity between the bend of the Main Marmara Fault near Istanbul and the Central basin to the relatively plane fault geometry of that segment. Normal stress on the Main Marmara Fault is highly variable along strike, which makes segment-wise rupture more likely than a rupture of the seismic gap at once. Comparably low normal stress on the Prince's Islands Segment indicates a shorter interevent time for this fault segment than for the central segment of the Main Marmara Fault.
Cheng-lu Gao - One of the best experts on this subject based on the ideXlab platform.
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A true triaxial Geomechanical Model test apparatus for studying the precursory information of water inrush from impermeable rock mass failure
Tunnelling and Underground Space Technology, 2019Co-Authors: Weimin Yang, Meixia Wang, Zongqing Zhou, Yuan Yongcai, Cheng-lu GaoAbstract:Abstract To study the precursory information of water inrush from impermeable rock mass failure, a true triaxial Geomechanical Model test apparatus was developed. The test apparatus designed is 5.5 m in length, 4.0 m in width and 2.5 m in height. It is mainly composed of a steel frame system, a hydraulic control system, a water pressure loading system and a data monitoring system. The main feature of the true triaxial Model test apparatus is its ability to apply high, uniform compressive loads in all three principal directions to perform tests under true triaxial static loading conditions. The apparatus can also be used to study the solid-fluid interaction of the surrounding rock mass and water. A test sample can be placed into and removed from the apparatus automatically and conveniently by hydraulic control software. A Model test of the water inrush in the Xiema Tunnel, which is located in Chongqing, China, was carried out by using this apparatus. The size of the experimental sample was 1500 × 1000 × 1000 mm. The variations in displacement, stress and seepage pressure were investigated. The test results indicate that the apparatus is stable and reliable.
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design of a displacement monitoring system based on optical grating and numerical verification in Geomechanical Model test of water leakage of tunnel
Geotechnical and Geological Engineering, 2018Co-Authors: Shangqu Sun, Zongqing Zhou, Shaoshuai Shi, Cheng-lu GaoAbstract:The displacement monitoring of surrounding rock is necessary in Geomechanical Model test. However, traditional monitoring technology is difficult to meet the needs of displacement monitoring in small geological Model tests. To solve the problems mentioned above, the authors developed a multi-point displacement monitoring system based on optical grating including multi-point extensometer, grating scale and multi-channel data acquisition system. Firstly, 3D anchor head with six barbs is designed and connected to the grating ruler by the steel wire, which proved to be rather sensitive to the rock deformation. Additionally, the displacement data collected can be transformed into electrical signal, which can be obtained by multi-channel acquisition system. Finally, the system was used in the Model test of tunnel water leakage. The designed anchors were pre-embedded in some key monitoring points around the section in order to investigate measurement of displacements in the lining during the loading of geostress and hydraulic pressure. Afterward, FLAC3D, the finite-difference method, is adopted to simulate the whole process of physical Model test and to compare with the experimental results. The results show that the experimental data was in good agreement with the numerical simulation results. In conclusion, the multi-point displacement monitoring system based on optical grating has higher precision and can be widely used in the physical Model test of geotechnical engineering.
Qiangyong Zhang - One of the best experts on this subject based on the ideXlab platform.
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true three dimensional Geomechanical Model tests for stability analysis of surrounding rock during the excavation of a deep underground laboratory
Rock Mechanics and Rock Engineering, 2020Co-Authors: Qiangyong Zhang, Chuancheng Liu, Kang Duan, Zhenjie Zhang, Wen XiangAbstract:Geological disposal at deep burial depths is a widely accepted method for the treatment of high-level radioactive waste, in which an underground laboratory is regarded as an essential facility to connect various aspects of the process. To evaluate the excavation-induced stability of the rock mass surrounding the underground laboratory for deep geological disposal of high-level radioactive waste in Beishan, Gansu Province, true three-dimensional Geomechanical Model tests are carried out for the first time. A Model test loading system is developed with an intelligent numerical control function and automatic excavation apparatuses. The variations in the displacement and stress surrounding the caverns are revealed. The test results indicate that after excavation, (1) the surrounding rock deforms toward the cavern with small displacements less than 3 mm; (2) the radial stress is lower, and the tangential stress is higher; tensile stress is induced in certain parts near the intersection of caverns but at a magnitude lower than the tensile strength of the rock; (3) the excavation-induced perturbation reaches approximately 1.5–2.0 times the cave diameter; and (4) the surrounding rock shows stability after excavation due to the favorable geological conditions and the overall high strength of the surrounding rock. Nevertheless, enhanced support via combined bolting and shotcrete are recommended at the crossing sections. The research results verify the rationality of the design scheme and provide important guidance for the construction of underground laboratories for deep underground disposal of high-level radioactive waste.
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Geomechanical Model Test and Energy Mechanism Analysis of Zonal Disintegration in Deep Surrounding Rock
Geosciences, 2018Co-Authors: Qiang Gao, Qiangyong Zhang, Xutao Zhang, Longyun ZhangAbstract:With the decreasing of shallow resources, underground roadways of resources exploitation have reached into deep rock mass with high geostress. A series of new failure phenomena such as zonal disintegration phenomenon were discovered in deep surrounding rock, which is completely different from shallow caverns. To reveal the formation mechanism of zonal disintegration, the Geomechanical Model test and energy mechanism analysis of zonal disintegration were carried out respectively. Taking the deep roadway of Dingji coal mine in China’s Huainan coal mine as engineering background, a 3D Geomechanical Model test was carried out relying on the high stress 3D loading test system. The zonal disintegration phenomenon was observed, and the oscillation law of displacement was measured. Based on the strain gradient theory and continuum damage mechanics, the elastoplastic damage Model was established. An energy failure criterion was proposed by principle of energy dissipation and release. The ODE45 function in Matlab software was used to solve the displacements and stresses of excavated Model roadway. The analytical solutions the and the Geomechanical Model test were basically consistent. The applicability of theoretical Model and energy failure criterion were confirmed to explain the mechanism of zonal disintegration and it can be used to provide theoretical support for the failure and supporting design of surrounding rock in deep underground engineering.
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failure mechanism and numerical simulation of zonal disintegration around a deep tunnel under high stress
International Journal of Rock Mechanics and Mining Sciences, 2017Co-Authors: Qiangyong Zhang, Xutao Zhang, Wen Xiang, Zhechao Wang, Junhua XueAbstract:Abstract The zonal disintegration phenomena in deep rock mass will appear with the increase of underground engineering depth which is widely different from shallow cavern. In order to reveal the formation mechanism of zonal disintegration, the Geomechanical Model test and numerical simulation of zonal disintegration are carried out respectively. Taking the deep tunnel of Dingji coal mine in China's Huainan coal mine as engineering background, a 3D Geomechanical Model test is carried out relying on the high stress 3D loading test system. The zonal disintegration phenomenon is observed, and the oscillation law of displacement and strain are measured. Based on the strain gradient theory and continuum damage mechanics, the zonal disintegration elastic damage-softening Model is established. The relationship between rock failure and energy dissipation is analyzed. According to the strain energy density theory, the zonal disintegration energy damage failure criterion based on strain gradient is established. A numerical analysis method for zonal disintegration is proposed, the zonal disintegration calculation program is developed based on a commercial finite element code. The results of numerical simulation and the 3D Geomechanical Model test are basically consistent.