When a porous rock is subjected to overall compressive loading,either increasing pore pressure or decreasing confining pressure could result in rock failure.The stress path and the applied pressure change rate may aff...When a porous rock is subjected to overall compressive loading,either increasing pore pressure or decreasing confining pressure could result in rock failure.The stress path and the applied pressure change rate may affect the initiation and propagation of fractures within brittle materials.Understanding the physical mechanisms leading to failure is crucial for underground engineering applications and geo-energy exploration and storage.We conducted triaxial compression experiments on porous Bentheim sandstone samples at different stress paths and pressure change rates.First,at a constant confining pressure of 35 MPa and pore pressure of 5 MPa,intact cylindrical samples were axially loaded up to about 85%of the peak strength.Subsequently,the axial piston position was fixed,and then either the pore pressure was increased or the confining pressure was decreased at two different rates(0.5 MPa/min or 2 MPa/min),leading to final catastrophic failure.The mechanical results revealed that samples subjected to higher rates of decreasing effective confining pressure exhibited larger stress drop rates,higher slip rates,higher total breakdown work,higher rates of acoustic emissions(AEs)before failure,and higher post-failure AE decay rates.In contrast,the applied stress path did not significantly affect rock failure characteristics.Comparison of located AE events with post-mortem microstructures of deformed samples shows a good agreement.The AE source type determined from the P-wave first-motion polarity shows that shear failure dominated the fracture process when approaching failure.Gutenberg-Richter b-values revealed a significant decrease before failure in all tests.Our results indicate that,in contrast to the stress path,the rate of effective stress change strongly affects fracturing behavior and AE rate changes.展开更多
Deep Earth exploration is a multi-disciplinary, complex activity aimed at understanding the structure, dynamics and evolution of the continents and their margins. Interaction between Earth's tectonic plates create...Deep Earth exploration is a multi-disciplinary, complex activity aimed at understanding the structure, dynamics and evolution of the continents and their margins. Interaction between Earth's tectonic plates created the continents and oceans that characterise our planet, while forming the mineral and other resources that support our living lives in modern society. Active tectonic processes are also responsible for devastating hazards such as earthquakes and volcanic eruptions, and control Earth's surface topography which fundamentally affects the climate and environment. Therefore, it is of common interest to society worldwide to study the interior of the Earth and to gain fundamental insight into how our planet operates.展开更多
The"DEEP"symposium aims to be a global forum for deep Earth exploration sponsored by China Geological Survey(CGS)and National Natural Science Foundation of China(NSFC),and co-supported by IUGS,ILP,ICDP,AGU,S...The"DEEP"symposium aims to be a global forum for deep Earth exploration sponsored by China Geological Survey(CGS)and National Natural Science Foundation of China(NSFC),and co-supported by IUGS,ILP,ICDP,AGU,SEG,GFZ,VSEGEI and other international organizations and agencies.The"DEEP"symposium is organized by the Sino Probe Center every two years.展开更多
文摘When a porous rock is subjected to overall compressive loading,either increasing pore pressure or decreasing confining pressure could result in rock failure.The stress path and the applied pressure change rate may affect the initiation and propagation of fractures within brittle materials.Understanding the physical mechanisms leading to failure is crucial for underground engineering applications and geo-energy exploration and storage.We conducted triaxial compression experiments on porous Bentheim sandstone samples at different stress paths and pressure change rates.First,at a constant confining pressure of 35 MPa and pore pressure of 5 MPa,intact cylindrical samples were axially loaded up to about 85%of the peak strength.Subsequently,the axial piston position was fixed,and then either the pore pressure was increased or the confining pressure was decreased at two different rates(0.5 MPa/min or 2 MPa/min),leading to final catastrophic failure.The mechanical results revealed that samples subjected to higher rates of decreasing effective confining pressure exhibited larger stress drop rates,higher slip rates,higher total breakdown work,higher rates of acoustic emissions(AEs)before failure,and higher post-failure AE decay rates.In contrast,the applied stress path did not significantly affect rock failure characteristics.Comparison of located AE events with post-mortem microstructures of deformed samples shows a good agreement.The AE source type determined from the P-wave first-motion polarity shows that shear failure dominated the fracture process when approaching failure.Gutenberg-Richter b-values revealed a significant decrease before failure in all tests.Our results indicate that,in contrast to the stress path,the rate of effective stress change strongly affects fracturing behavior and AE rate changes.
文摘Deep Earth exploration is a multi-disciplinary, complex activity aimed at understanding the structure, dynamics and evolution of the continents and their margins. Interaction between Earth's tectonic plates created the continents and oceans that characterise our planet, while forming the mineral and other resources that support our living lives in modern society. Active tectonic processes are also responsible for devastating hazards such as earthquakes and volcanic eruptions, and control Earth's surface topography which fundamentally affects the climate and environment. Therefore, it is of common interest to society worldwide to study the interior of the Earth and to gain fundamental insight into how our planet operates.
文摘The"DEEP"symposium aims to be a global forum for deep Earth exploration sponsored by China Geological Survey(CGS)and National Natural Science Foundation of China(NSFC),and co-supported by IUGS,ILP,ICDP,AGU,SEG,GFZ,VSEGEI and other international organizations and agencies.The"DEEP"symposium is organized by the Sino Probe Center every two years.
