Rockburst disasters occur frequently during deep underground excavation,yet traditional concepts and methods can hardly meet the requirements for support under high geo-stress conditions.Consequently,rockburst control...Rockburst disasters occur frequently during deep underground excavation,yet traditional concepts and methods can hardly meet the requirements for support under high geo-stress conditions.Consequently,rockburst control remains challenging in the engineering field.In this study,the mechanism of excavation-induced rockburst was briefly described,and it was proposed to apply the excavation compensation method(ECM)to rockburst control.Moreover,a field test was carried out on the Qinling Water Conveyance Tunnel.The following beneficial findings were obtained:Excavation leads to changes in the engineering stress state of surrounding rock and results in the generation of excess energy DE,which is the fundamental cause of rockburst.The ECM,which aims to offset the deep excavation effect and lower the risk of rockburst,is an active support strategy based on high pre-stress compensation.The new negative Poisson’s ratio(NPR)bolt developed has the mechanical characteristics of high strength,high toughness,and impact resistance,serving as the material basis for the ECM.The field test results reveal that the ECM and the NPR bolt succeed in controlling rockburst disasters effectively.The research results are expected to provide guidance for rockburst support in deep underground projects such as Sichuan-Xizang Railway.展开更多
Cavitation is a prevalent phenomenon within the domain of ship and ocean engineering,predominantly occurring in the tail flow fields of high-speed rotating propellers and on the surfaces of high-speed underwater vehic...Cavitation is a prevalent phenomenon within the domain of ship and ocean engineering,predominantly occurring in the tail flow fields of high-speed rotating propellers and on the surfaces of high-speed underwater vehicles.The re-entrant jet and compression wave resulting from the collapse of cavity vapour are pivotal factors contributing to cavity instability.Concurrently,these phenomena significantly modulate the evolution of cavitation flow.In this paper,numerical investigations into cloud cavitation over a Clark-Y hydrofoil were conducted,utilizing the Large Eddy Simulation(LES)turbulence model and the Volume of Fluid(VOF)method within the OpenFOAM framework.Comparative analysis of results obtained at different angles of attack is undertaken.A discernible augmentation in cavity thickness is observed concomitant with the escalation in attack angle,alongside a progressive intensification in pressure at the leading edge of the hydrofoil,contributing to the suction force.These results can serve as a fundamental point of reference for gaining a deeper comprehension of cloud cavitation dynamics.展开更多
The recent report of superconductivity in nitrogen-doped lutetium hydride(Lu-H-N)at 294 K and 1 GPa brought hope for long-sought-after ambient-condition superconductors.However,the failure of scientists worldwide to i...The recent report of superconductivity in nitrogen-doped lutetium hydride(Lu-H-N)at 294 K and 1 GPa brought hope for long-sought-after ambient-condition superconductors.However,the failure of scientists worldwide to independently reproduce these results has cast intense skepticism on this exciting claim.In this work,using a reliable experimental protocol,we synthesized Lu-H-N while minimizing extrinsic influences and reproduced the sudden change in resistance near room temperature.With quantitative comparison of the temperaturedependent resistance between Lu-H-N and the pure lutetium before reaction,we were able to clarify that the drastic resistance change is most likely caused by a metal-to-poor-conductor transition rather than by superconductivity.Herein,we also briefly discuss other issues recently raised in relation to the Lu-H-N system.展开更多
Particle breakage commonly occurs during processing of particulate materials,but a mechanistic model of particle impact breakage is not fully established.This article presents oblique impact breakage characteristics o...Particle breakage commonly occurs during processing of particulate materials,but a mechanistic model of particle impact breakage is not fully established.This article presents oblique impact breakage characteristics of nonspherical particles using discrete element method(DEM)simulations.Three different particle shapes,i.e.spherical,cuboidal and cylindrical,are investigated.Constituent spheres are agglomerated with bridging bonds to model the breakage characteristics under impact conditions.The effect of agglomerate shapes on the breakage pattern,damage ratio,and fragment size distribution is fully investigated.By using a newly proposed oblique impact model,unified breakage master surfaces are theoretically constructed for all the particle shapes under oblique impact conditions.The developed approach can be applied to modelling particulate processes where nonspherical particles and oblique impact breakage are prevailing.展开更多
基金supported by the National Natural Science Foundation of China (41941018)the Foundation of State Key Laboratory for Geomechanics and Deep Underground Engineering (SKLGDUEK 2217)the Foundation of Collaborative Innovation Center for Prevention and Control of Mountain Geological Hazards of Zhejiang Province (PCMGH-2022-03).
文摘Rockburst disasters occur frequently during deep underground excavation,yet traditional concepts and methods can hardly meet the requirements for support under high geo-stress conditions.Consequently,rockburst control remains challenging in the engineering field.In this study,the mechanism of excavation-induced rockburst was briefly described,and it was proposed to apply the excavation compensation method(ECM)to rockburst control.Moreover,a field test was carried out on the Qinling Water Conveyance Tunnel.The following beneficial findings were obtained:Excavation leads to changes in the engineering stress state of surrounding rock and results in the generation of excess energy DE,which is the fundamental cause of rockburst.The ECM,which aims to offset the deep excavation effect and lower the risk of rockburst,is an active support strategy based on high pre-stress compensation.The new negative Poisson’s ratio(NPR)bolt developed has the mechanical characteristics of high strength,high toughness,and impact resistance,serving as the material basis for the ECM.The field test results reveal that the ECM and the NPR bolt succeed in controlling rockburst disasters effectively.The research results are expected to provide guidance for rockburst support in deep underground projects such as Sichuan-Xizang Railway.
基金supported by the National Natural Science Foundation of China(Nos.12202011,12332014)China Postdoctoral Science Foundation(No.2022M710190).
文摘Cavitation is a prevalent phenomenon within the domain of ship and ocean engineering,predominantly occurring in the tail flow fields of high-speed rotating propellers and on the surfaces of high-speed underwater vehicles.The re-entrant jet and compression wave resulting from the collapse of cavity vapour are pivotal factors contributing to cavity instability.Concurrently,these phenomena significantly modulate the evolution of cavitation flow.In this paper,numerical investigations into cloud cavitation over a Clark-Y hydrofoil were conducted,utilizing the Large Eddy Simulation(LES)turbulence model and the Volume of Fluid(VOF)method within the OpenFOAM framework.Comparative analysis of results obtained at different angles of attack is undertaken.A discernible augmentation in cavity thickness is observed concomitant with the escalation in attack angle,alongside a progressive intensification in pressure at the leading edge of the hydrofoil,contributing to the suction force.These results can serve as a fundamental point of reference for gaining a deeper comprehension of cloud cavitation dynamics.
文摘The recent report of superconductivity in nitrogen-doped lutetium hydride(Lu-H-N)at 294 K and 1 GPa brought hope for long-sought-after ambient-condition superconductors.However,the failure of scientists worldwide to independently reproduce these results has cast intense skepticism on this exciting claim.In this work,using a reliable experimental protocol,we synthesized Lu-H-N while minimizing extrinsic influences and reproduced the sudden change in resistance near room temperature.With quantitative comparison of the temperaturedependent resistance between Lu-H-N and the pure lutetium before reaction,we were able to clarify that the drastic resistance change is most likely caused by a metal-to-poor-conductor transition rather than by superconductivity.Herein,we also briefly discuss other issues recently raised in relation to the Lu-H-N system.
基金the financial support from National Natural Science Foundation of China Excellent Young Scientists Fund Program(Overseas)(grant No.YQ2023-22)Shandong Excellent YoungsScientistsFund Program(Overseas)(grant No.2022HWYQ-020)Shenzhen Science and TechnologyProgram(grant No.RCBS20200714114910354,JCYJ20220530141016036 and GJHZ20200731095006019).
文摘Particle breakage commonly occurs during processing of particulate materials,but a mechanistic model of particle impact breakage is not fully established.This article presents oblique impact breakage characteristics of nonspherical particles using discrete element method(DEM)simulations.Three different particle shapes,i.e.spherical,cuboidal and cylindrical,are investigated.Constituent spheres are agglomerated with bridging bonds to model the breakage characteristics under impact conditions.The effect of agglomerate shapes on the breakage pattern,damage ratio,and fragment size distribution is fully investigated.By using a newly proposed oblique impact model,unified breakage master surfaces are theoretically constructed for all the particle shapes under oblique impact conditions.The developed approach can be applied to modelling particulate processes where nonspherical particles and oblique impact breakage are prevailing.