The combination of the dipping effect and hydromechanical(H-M)coupling effect can easily lead to water inrush disasters in water-rich roadways with different dip angles in coal mines.Therefore,H-M coupling tests of be...The combination of the dipping effect and hydromechanical(H-M)coupling effect can easily lead to water inrush disasters in water-rich roadways with different dip angles in coal mines.Therefore,H-M coupling tests of bedded sandstones under identical osmotic pressure and various confining pressures were conducted.Then,the evolution curves of stress-strain,permeability and damage,macro-and mesoscopic failure characteristics were obtained.Subsequently,the mechanical behaviour was characterized,and finally the failure mechanism was revealed.The results showed that:(1)The failure of the sandstone with the bedding angle of 45°or 60°was the structure-dominant type,while that with the bedding angle of 0°,30°or 90°was the force-dominant type.(2)When the bedding angle was in the range of(0°,30°)or(45°,90°),the confining pressure played a dominant role in influencing the peak strength.However,withinβ∈(30°,45°),the bedding effect played a dominant role in the peak strength.(3)With the increase in bedding angle,the cohesion increased first,then decreased and finally increased,while the internal friction angle was the opposite.(4)When the bedding angle was 0°or 30°,the“water wedging”effect and the“bedding buckling”effect would lead to the forking or converging shear failure.When the bedding angle was 45°or 60°,the sliding friction effect would lead to the shear slipping failure.When the bedding angle was 90°,the combination of the“bedding buckling”effect and shear effect would lead to the mixed tension-shear failure.The above conclusions obtained are helpful for the prevention of water inrush disasters in water-rich roadways with different dips in coal mines.展开更多
Water reinjection into the formation is an indispensable operation in many energy engineering practices.This operation involves a complex hydromechanical(HM)coupling process and sometimes even causes unpredictable dis...Water reinjection into the formation is an indispensable operation in many energy engineering practices.This operation involves a complex hydromechanical(HM)coupling process and sometimes even causes unpredictable disasters,such as induced seismicity.It is acknowledged that the relative magnitude and direction of the principal stresses significantly influence the HM behaviors of rocks during injection.However,due to the limitations of current testing techniques,it is still difficult to comprehensively conduct laboratory injection tests under various stress conditions,such as in triaxial extension stress states.To this end,a numerical study of HM changes in rocks during injection under different stress states is conducted.In this model,the saturated rock is first loaded to the target stress state under drainage conditions,and then the stress state is maintained and water is injected from the top to simulate the formation injection operation.Particular attention is given to the difference in HM changes under triaxial compression and extension stresses.This includes the differences in the pore pressure propagation,mean effective stress,volumetric strain,and stress-induced permeability.The numerical results demonstrate that the differential stress will significantly affect the HM behaviors of rocks,but the degree of influence is different under the two triaxial stress states.The HM changes caused by the triaxial compression stress states are generally greater than those of extension,but the differences decrease with increasing differential stress,indicating that the increase in the differential stress will weaken the impact of the stress state on the HM response.In addition,the shear failure potential of fracture planes with various inclination angles is analyzed and summarized under different stress states.It is recommended that engineers could design suitable injection schemes according to different tectonic stress fields versus fault occurrence to reduce the risk of injection-induced seismicity.展开更多
Natural rock joint permeability deviates from the classic fluid flow governing equations due to the inher-ent fracture surface roughness(i.e.,contact points,spatial correlation,matching,varying aperture,iso-lated void...Natural rock joint permeability deviates from the classic fluid flow governing equations due to the inher-ent fracture surface roughness(i.e.,contact points,spatial correlation,matching,varying aperture,iso-lated voids,infilling material,tortuosity and channellings)and engineering disturbance such as excavations.To improve the accuracy of fracture permeability evaluation,many efforts have been made in analytical,experimental,and numerical methods.This study reviews the modified mathematical gov-erning equations of fluid flow and classifies them based on different influencing factors,such as friction factor,aperture,tortuosity,inertia,and various in situ stress effects.Various experimental and simulation techniques for the coupled normal-and shear-stress flow problems were assessed,and their advantages and disadvantages were also analysed.Furthermore,different surface roughness descriptions and their impacts on mechanical and hydraulic behaviours were discussed,followed by the potential research directions for fracture flow problems.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.52034009 and 51974319)the Yue Qi Distinguished Scholar Project(Grant No.2020JCB01).
文摘The combination of the dipping effect and hydromechanical(H-M)coupling effect can easily lead to water inrush disasters in water-rich roadways with different dip angles in coal mines.Therefore,H-M coupling tests of bedded sandstones under identical osmotic pressure and various confining pressures were conducted.Then,the evolution curves of stress-strain,permeability and damage,macro-and mesoscopic failure characteristics were obtained.Subsequently,the mechanical behaviour was characterized,and finally the failure mechanism was revealed.The results showed that:(1)The failure of the sandstone with the bedding angle of 45°or 60°was the structure-dominant type,while that with the bedding angle of 0°,30°or 90°was the force-dominant type.(2)When the bedding angle was in the range of(0°,30°)or(45°,90°),the confining pressure played a dominant role in influencing the peak strength.However,withinβ∈(30°,45°),the bedding effect played a dominant role in the peak strength.(3)With the increase in bedding angle,the cohesion increased first,then decreased and finally increased,while the internal friction angle was the opposite.(4)When the bedding angle was 0°or 30°,the“water wedging”effect and the“bedding buckling”effect would lead to the forking or converging shear failure.When the bedding angle was 45°or 60°,the sliding friction effect would lead to the shear slipping failure.When the bedding angle was 90°,the combination of the“bedding buckling”effect and shear effect would lead to the mixed tension-shear failure.The above conclusions obtained are helpful for the prevention of water inrush disasters in water-rich roadways with different dips in coal mines.
基金funded by the National Natural Science Foundation of China(Grant Nos.41872210 and 41902297)IRSMGFZ Subsurface Utilization of Captured Carbon and Energy Storage System and the Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering(Grant No.Z018004).
文摘Water reinjection into the formation is an indispensable operation in many energy engineering practices.This operation involves a complex hydromechanical(HM)coupling process and sometimes even causes unpredictable disasters,such as induced seismicity.It is acknowledged that the relative magnitude and direction of the principal stresses significantly influence the HM behaviors of rocks during injection.However,due to the limitations of current testing techniques,it is still difficult to comprehensively conduct laboratory injection tests under various stress conditions,such as in triaxial extension stress states.To this end,a numerical study of HM changes in rocks during injection under different stress states is conducted.In this model,the saturated rock is first loaded to the target stress state under drainage conditions,and then the stress state is maintained and water is injected from the top to simulate the formation injection operation.Particular attention is given to the difference in HM changes under triaxial compression and extension stresses.This includes the differences in the pore pressure propagation,mean effective stress,volumetric strain,and stress-induced permeability.The numerical results demonstrate that the differential stress will significantly affect the HM behaviors of rocks,but the degree of influence is different under the two triaxial stress states.The HM changes caused by the triaxial compression stress states are generally greater than those of extension,but the differences decrease with increasing differential stress,indicating that the increase in the differential stress will weaken the impact of the stress state on the HM response.In addition,the shear failure potential of fracture planes with various inclination angles is analyzed and summarized under different stress states.It is recommended that engineers could design suitable injection schemes according to different tectonic stress fields versus fault occurrence to reduce the risk of injection-induced seismicity.
文摘Natural rock joint permeability deviates from the classic fluid flow governing equations due to the inher-ent fracture surface roughness(i.e.,contact points,spatial correlation,matching,varying aperture,iso-lated voids,infilling material,tortuosity and channellings)and engineering disturbance such as excavations.To improve the accuracy of fracture permeability evaluation,many efforts have been made in analytical,experimental,and numerical methods.This study reviews the modified mathematical gov-erning equations of fluid flow and classifies them based on different influencing factors,such as friction factor,aperture,tortuosity,inertia,and various in situ stress effects.Various experimental and simulation techniques for the coupled normal-and shear-stress flow problems were assessed,and their advantages and disadvantages were also analysed.Furthermore,different surface roughness descriptions and their impacts on mechanical and hydraulic behaviours were discussed,followed by the potential research directions for fracture flow problems.