‘Coupled process’ implies that one process affects the initiation and progress of the others and vice versa. The deformation and damage behaviors of rock under loading process change the fluid flow field within it, and lead to altering in permeable characteristics; on the other side inner fluid flow leads to altering in pore pressure and effective stress of rock matrix and flow by influencing stress strain behavior of rock. Therefore, responses of rock to natural or man-made perturbations cannot be predicted with confidence by considering each process independently. As far as hydro-mechanical behavior of rock is concerned, the researchers have always been making efforts to develop the model which can represent the permeable characteristics as well as stress-strain behaviors during the entire damage process. A brittle low porous granite was chosen as the study object in this thesis, the aim is to establish a corresponding constitutive law including the relation between permeability evolution and mechanical deformation as well as the rock failure behavior under hydro-mechanical coupled conditions based on own hydro-mechanical coupled lab tests. The main research works of this thesis are as follows: 1. The fluid flow and mechanical theoretical models have been reviewed and the theoretical methods to solve hydro-mechanical coupled problems of porous medium such as flow equations, elasto-plastic constitutive law, and Biot coupled control equations have been summarized. 2. A series of laboratory tests have been conducted on the granite from Erzgebirge–Vogtland region within the Saxothuringian segment of Central Europe, including: permeability measurements, ultrasonic wave speed measurements, Brazilian tests, uniaxial and triaxial compression tests. A hydro-mechanical coupled testing system has been designed and used to conduct drained, undrained triaxial compression tests and permeability evolution measurements during complete loading process. A set of physical and mechanical parameters were obtained. 3. Based on analyzing the complete stress-strain curves obtained from triaxial compression tests and Hoek-Brown failure criterion, a modified elemental elasto-plastic constitutive law was developed which can represent strength degradation and volume dilation considering the influence of confining pressure. 4. The mechanism of HM-coupled behavior according to the Biot theory of elastic porous medium is summarized. A trilinear evolution rule for Biot’s coefficient based on the laboratory observations was deduced to eliminate the error in predicting rock strength caused by constant Biot’s coefficient. 5. The permeability evolution of low porous rock during the failure process was described based on literature data and own measurements, a general rule for the permeability evolution was developed for the laboratory scale, a strong linear relation between permeability and volumetrical strain was observed and a linear function was extracted to predict permeability evolution during loading process based on own measurements. 6. By combining modified constitutive law, the trilinear Biot’s coefficient evolution model and the linear relationship between permeability and volumetrical strain, a fully hydro-mechanical coupled numerical simulation scheme was developed and implemented in FLAC3D. A series of numerical simulations of triaxial compression test considering the hydro-mechanical coupling were performed with FLAC3D. And a good agreement was found between the numerical simulation results and the laboratory measurements under 20 MPa confining pressure and 10 MPa fluid pressure, the feasibility of this fully hydro-mechanical coupled model was proven.

‘Coupled process’ implies that one process affects the initiation and progress of the others and vice versa. The deformation and damage behaviors of rock under loading process change the fluid flow field within it, and lead to altering in permeable characteristics; on the other side inner fluid flow leads to altering in pore pressure and effective stress of rock matrix and flow by influencing stress strain behavior of rock. Therefore, responses of rock to natural or man-made perturbations cannot be predicted with confidence by considering each process independently. As far as hydro-mechanical behavior of rock is concerned, the researchers have always been making efforts to develop the model which can represent the permeable characteristics as well as stress-strain behaviors during the entire damage process. A brittle low porous granite was chosen as the study object in this thesis, the aim is to establish a corresponding constitutive law including the relation between permeability evolution and mechanical deformation as well as the rock failure behavior under hydro-mechanical coupled conditions based on own hydro-mechanical coupled lab tests. The main research works of this thesis are as follows: 1. The fluid flow and mechanical theoretical models have been reviewed and the theoretical methods to solve hydro-mechanical coupled problems of porous medium such as flow equations, elasto-plastic constitutive law, and Biot coupled control equations have been summarized. 2. A series of laboratory tests have been conducted on the granite from Erzgebirge–Vogtland region within the Saxothuringian segment of Central Europe, including: permeability measurements, ultrasonic wave speed measurements, Brazilian tests, uniaxial and triaxial compression tests. A hydro-mechanical coupled testing system has been designed and used to conduct drained, undrained triaxial compression tests and permeability evolution measurements during complete loading process. A set of physical and mechanical parameters were obtained. 3. Based on analyzing the complete stress-strain curves obtained from triaxial compression tests and Hoek-Brown failure criterion, a modified elemental elasto-plastic constitutive law was developed which can represent strength degradation and volume dilation considering the influence of confining pressure. 4. The mechanism of HM-coupled behavior according to the Biot theory of elastic porous medium is summarized. A trilinear evolution rule for Biot’s coefficient based on the laboratory observations was deduced to eliminate the error in predicting rock strength caused by constant Biot’s coefficient. 5. The permeability evolution of low porous rock during the failure process was described based on literature data and own measurements, a general rule for the permeability evolution was developed for the laboratory scale, a strong linear relation between permeability and volumetrical strain was observed and a linear function was extracted to predict permeability evolution during loading process based on own measurements. 6. By combining modified constitutive law, the trilinear Biot’s coefficient evolution model and the linear relationship between permeability and volumetrical strain, a fully hydro-mechanical coupled numerical simulation scheme was developed and implemented in FLAC3D. A series of numerical simulations of triaxial compression test considering the hydro-mechanical coupling were performed with FLAC3D. And a good agreement was found between the numerical simulation results and the laboratory measurements under 20 MPa confining pressure and 10 MPa fluid pressure, the feasibility of this fully hydro-mechanical coupled model was proven.

Geotechnische Problem- und Fragestellungen befassen sich zunehmend mit der komplexen Interaktion unterschiedlicher physikalischer Prozesse. Ein Beispiel sind hydro-mechanische Wechselwirkungen, die in verschiedenen Anwendungsbereichen eine große Rolle spielen (Hydraulic Fracturing, Bewertung von Barriereintegrität, Böschungsanalysen, etc.). Numerische Simulationen helfen dabei, umfangreiche multiphysikalische Vorgänge abzubilden. Zur hinreichend genauen und effizienten Bearbeitung kann es jedoch sein, dass die Anwendung eines einzelnen spezialisierten Softwarepaketes nicht ausreicht und nur Softwarekopplungen Abhilfe schaffen. Die vorliegende Arbeit erweitert die geomechanische Komplexität einer hydro-mechanischen Kopplung auf visko-elasto-plastisches Materialverhalten im Salinar. Betrachtet werden langandauernde und großräumig induzierte Fluidbewegungen in den durch Volumenkonvergenz charakterisierten lösungserfüllten Abbauen in einem generischen Kali- bzw. Steinsalzbergwerk. Zur Bearbeitung der Problemstellung wird eine grundlegende Methode zur Kopplung der numerischen Codes FLAC3D und Ansys Fluent entwickelt, detailliert vorgestellt und verifiziert. Unterschiedliche Modellszenarien in Bezug auf die initiale Fluidverteilung simulieren eindrucksvoll das Strömungsverhalten im generischen Grubenmodell unter Ausbildung eines freien Fluidspiegels oder eines Überdrucks im eingeschlossenen Fluid. Die Ergebnisse werden umfassend analysiert und das Potenzial zu Effizienzsteigerung durch die Softwarekopplung aufgezeigt. / Geotechnical problems and questions are progressively dealing with complex interactions of different physical processes. An example is hydro-mechanical coupling playing an important role in various research topics and applications (e.g. hydraulic fracturing, assessment of barrier integrity and slope analysis). Numerical simulations help to model extensive multi-physical processes. However, for an accurate and efficient processing, using a single specialized numerical code may not be sufficient and solutions can be obtained only with software couplings. The presented work extends the geomechanically complexity of a hydro-mechanical coupling by visco-elasto-plastic material behaviour in salt formations considering long-lasting and large-scale induced fluid flow within solution-filled cavities in a generic potash or rock salt mine, due to volume convergence. For solving this problem, a basic method for coupling the numerical codes FLAC3D and Ansys Fluent is developed, presented, and verified in detail. Different model scenarios in respect to initial fluid saturation are simulating the fluid flow in the generic mine model, depicting either a free fluid surface or an excess pressure in the trapped fluid. The results are analysed, and the potential for the increase of efficiency through the software coupling of FLAC3D and Ansys Fluent is demonstrated.