Understanding the anchorage performance of en-echelon joints under cyclic shear loading is crucial for optimizing support strategies in jointed rock masses.This study examines the anchorage effects on enechelon joints...Understanding the anchorage performance of en-echelon joints under cyclic shear loading is crucial for optimizing support strategies in jointed rock masses.This study examines the anchorage effects on enechelon joints with various orientations using laboratory cyclic shear tests.By comparing unbolted and bolted en-echelon joints,we analyze shear zone damage,shear properties,dilatancy,energy absorption,and acoustic emission characteristics to evaluate anchoring effects across shear cycles and joint orientations.Results reveal that bolted en-echelon joints experience more severe shear zone damage after cycles,with bolt deformation correlating to shear zone width.Bolted en-echelon joints exhibit faster shear strength deterioration and higher cumulative strength loss compared to unbolted ones,with losses ranging from 20.04%to 72.76%.The compressibility of en-echelon joints reduces the anchoring effect during shear cycles,leading to lower shear strength of bolted en-echelon joints in later stages of shear cycles compared to unbolted ones.Bolts reinforce en-echelon joints more effectively at non-positive angles,with the best performance observed at 0°and-60°.Anchorage accelerates the transition from rolling friction to sliding friction in the shear zone,enhancing energy absorption,which is crucial for rock projects under dynamic shear loading.Additionally,rock bolts expedite the transition of the cumulative AE hits and cumulative AE energy curves from rapid to steady growth,indicating that strong bolt-rock interactions accelerate crack initiation,propagation,and energy release.展开更多
This study aims to understand the effect of injection rate on injection-induced fracture activation in granite.We performed water injection-induced slip tests on samples containing either a smooth or a rough fracture ...This study aims to understand the effect of injection rate on injection-induced fracture activation in granite.We performed water injection-induced slip tests on samples containing either a smooth or a rough fracture at four different injection rates under undrained conditions and monitored the acoustic emission(AE)signals during the tests.Experimental results reveal that the critical activation fluid pressure is related to the injection rate,pressure diffusion rate,stress state,and fracture roughness.For the smooth fracture,as the injection rate increases,the critical activation fluid pressure increases significantly,while the injection rate has little effect on the critical activation fluid pressure of the rough fracture.The quasi-static slip distance of fractures decreases as the injection rate increases,with rough fractures exhibiting a greater overall slip distance compared to smooth fractures.The number of AE events per unit sliding distance increases with the injection rate,while the global b value decreases.These results indicate that higher injection rates produce more large-magnitude AE events and more severe slip instability and asperity damage.We established a linkage between fluid injection volume,injection rate,and AE events using the seismogenic index(Σ).The smooth fracture exhibits a steadily increasingΣwith the elapse of injection time,and the rate of increase is higher at higher injection rates;while the rough fracture is featured by a fluctuatingΣ,signifying the intermittent occurrence of large-magnitude AE events associated with the damage of larger fracture asperities.Our results highlight the importance of fracture surface heterogeneity on injection-induced fracture activation and slip.展开更多
Damage in a rock mass is heavily dependent on the existence and growth of joints,which are also influenced by the complex stress states induced by human activities(e.g.,tunneling and excavation).A proper representatio...Damage in a rock mass is heavily dependent on the existence and growth of joints,which are also influenced by the complex stress states induced by human activities(e.g.,tunneling and excavation).A proper representation of the loading path is essential for understanding the mechanical behaviors of rock masses.Based on the discrete element method(DEM),the influence of the loading path on the cracking process of a rock specimen containing an open flaw is examined.The effectiveness of the model is confirmed by comparing the simulation results under a uniaxial compression test to existing research findings,where wing crack initiates first and secondary cracks contribute to the failure of the specimen.Simulation results confirm that the cracking process is dependent upon both the confining pressure and the loading path.Under the axial loading test,a higher confining pressure suppresses the development of tensile wing cracks and forces the formation of secondary cracks in the form of shear bands perpendicular to the flaw.Increase of confining pressure also decreases the influence of the loading path on the cracking process.Reduction of confining pressure during an unloading test amplifies the concentration of tensile stress and ultimately promotes the appearance of a tensile splitting fracture at meso-scale.Confining pressure at the failure stage is well predicted by the Hoek-Brown failure criterion under quasi-static conditions.展开更多
The widely used clustered regularly interspaced short palindromic repeats(CRISPR)/CRISPR-associated nuclease(Cas)system is thought to have evolved from IS200/IS605 transposons.TnpB proteins,encoded by one type of IS20...The widely used clustered regularly interspaced short palindromic repeats(CRISPR)/CRISPR-associated nuclease(Cas)system is thought to have evolved from IS200/IS605 transposons.TnpB proteins,encoded by one type of IS200/IS605 transposon,are considered to be the evolutionary ancestors of Cas12 nucleases,which have been engineered to function as RNA-guided DNA endonucleases for genome editing in bacteria and human cells.TnpB nucleases,which are smaller than Cas nucleases,have been engineered for use in genome editing in animal systems,but the feasibility of this approach in plants remained unknown.Here,we obtained stably transformed genome-edited mutants in rice(Oryza sativa)by adapting three recently identified TnpB genome editing vectors,encoding distinct TnpB nucleases(ISAam1,ISDra2,and ISYmu1),for use in plants,demonstrating that the hypercompact TnpB proteins can effectively edit plant genomes.ISDra2 and ISYmu1 precisely edited their target sequences,with no off-target mutations detected,showing that TnpB transposon nucleases are suitable for development into a new genome editing tool for plants.Future modifications improving the genome-editing efficiency of the TnpB system will facilitate plant functional studies and breeding programs.展开更多
基金financially supported by the National Natural Science Foundation of China (No.42172292)Taishan Scholars Project Special Funding,and Shandong Energy Group (No.SNKJ2022A01-R26)funded by the China Scholarship Council (CSC No.202006220274)。
文摘Understanding the anchorage performance of en-echelon joints under cyclic shear loading is crucial for optimizing support strategies in jointed rock masses.This study examines the anchorage effects on enechelon joints with various orientations using laboratory cyclic shear tests.By comparing unbolted and bolted en-echelon joints,we analyze shear zone damage,shear properties,dilatancy,energy absorption,and acoustic emission characteristics to evaluate anchoring effects across shear cycles and joint orientations.Results reveal that bolted en-echelon joints experience more severe shear zone damage after cycles,with bolt deformation correlating to shear zone width.Bolted en-echelon joints exhibit faster shear strength deterioration and higher cumulative strength loss compared to unbolted ones,with losses ranging from 20.04%to 72.76%.The compressibility of en-echelon joints reduces the anchoring effect during shear cycles,leading to lower shear strength of bolted en-echelon joints in later stages of shear cycles compared to unbolted ones.Bolts reinforce en-echelon joints more effectively at non-positive angles,with the best performance observed at 0°and-60°.Anchorage accelerates the transition from rolling friction to sliding friction in the shear zone,enhancing energy absorption,which is crucial for rock projects under dynamic shear loading.Additionally,rock bolts expedite the transition of the cumulative AE hits and cumulative AE energy curves from rapid to steady growth,indicating that strong bolt-rock interactions accelerate crack initiation,propagation,and energy release.
基金supported by the National Key Research and Development Program of China(Grant No.2023YFB2390300)the National Natural Science Foundation of China(Grant No.42172292)Yinlin Ji is grateful for the support by the Helmholtz Association's Initiative and Networking Fund for the Helmholtz Young Investigator Group ARES(Contract No.VH-NG-1516).
文摘This study aims to understand the effect of injection rate on injection-induced fracture activation in granite.We performed water injection-induced slip tests on samples containing either a smooth or a rough fracture at four different injection rates under undrained conditions and monitored the acoustic emission(AE)signals during the tests.Experimental results reveal that the critical activation fluid pressure is related to the injection rate,pressure diffusion rate,stress state,and fracture roughness.For the smooth fracture,as the injection rate increases,the critical activation fluid pressure increases significantly,while the injection rate has little effect on the critical activation fluid pressure of the rough fracture.The quasi-static slip distance of fractures decreases as the injection rate increases,with rough fractures exhibiting a greater overall slip distance compared to smooth fractures.The number of AE events per unit sliding distance increases with the injection rate,while the global b value decreases.These results indicate that higher injection rates produce more large-magnitude AE events and more severe slip instability and asperity damage.We established a linkage between fluid injection volume,injection rate,and AE events using the seismogenic index(Σ).The smooth fracture exhibits a steadily increasingΣwith the elapse of injection time,and the rate of increase is higher at higher injection rates;while the rough fracture is featured by a fluctuatingΣ,signifying the intermittent occurrence of large-magnitude AE events associated with the damage of larger fracture asperities.Our results highlight the importance of fracture surface heterogeneity on injection-induced fracture activation and slip.
基金supported by the Shandong Provincial Natural Science Foundation of China(No.ZR2020YQ44)the National Natural Science Foundation of China(No.51909138)。
文摘Damage in a rock mass is heavily dependent on the existence and growth of joints,which are also influenced by the complex stress states induced by human activities(e.g.,tunneling and excavation).A proper representation of the loading path is essential for understanding the mechanical behaviors of rock masses.Based on the discrete element method(DEM),the influence of the loading path on the cracking process of a rock specimen containing an open flaw is examined.The effectiveness of the model is confirmed by comparing the simulation results under a uniaxial compression test to existing research findings,where wing crack initiates first and secondary cracks contribute to the failure of the specimen.Simulation results confirm that the cracking process is dependent upon both the confining pressure and the loading path.Under the axial loading test,a higher confining pressure suppresses the development of tensile wing cracks and forces the formation of secondary cracks in the form of shear bands perpendicular to the flaw.Increase of confining pressure also decreases the influence of the loading path on the cracking process.Reduction of confining pressure during an unloading test amplifies the concentration of tensile stress and ultimately promotes the appearance of a tensile splitting fracture at meso-scale.Confining pressure at the failure stage is well predicted by the Hoek-Brown failure criterion under quasi-static conditions.
文摘The widely used clustered regularly interspaced short palindromic repeats(CRISPR)/CRISPR-associated nuclease(Cas)system is thought to have evolved from IS200/IS605 transposons.TnpB proteins,encoded by one type of IS200/IS605 transposon,are considered to be the evolutionary ancestors of Cas12 nucleases,which have been engineered to function as RNA-guided DNA endonucleases for genome editing in bacteria and human cells.TnpB nucleases,which are smaller than Cas nucleases,have been engineered for use in genome editing in animal systems,but the feasibility of this approach in plants remained unknown.Here,we obtained stably transformed genome-edited mutants in rice(Oryza sativa)by adapting three recently identified TnpB genome editing vectors,encoding distinct TnpB nucleases(ISAam1,ISDra2,and ISYmu1),for use in plants,demonstrating that the hypercompact TnpB proteins can effectively edit plant genomes.ISDra2 and ISYmu1 precisely edited their target sequences,with no off-target mutations detected,showing that TnpB transposon nucleases are suitable for development into a new genome editing tool for plants.Future modifications improving the genome-editing efficiency of the TnpB system will facilitate plant functional studies and breeding programs.
