Vertical backfill drill-hole is usually a key project in an underground mine with backfill method and can be easily damaged by impact of backfill slurry.Observation of the damaged vertical backfill drill-holes in Jinc...Vertical backfill drill-hole is usually a key project in an underground mine with backfill method and can be easily damaged by impact of backfill slurry.Observation of the damaged vertical backfill drill-holes in Jinchuan Nonferrous Metal Corporation（JNMC）,Gansu Province,China,given by a digital drill-hole video camera,indicated that there usually exist serious wear zones in casing pipe in vertical backfill drill-hole（CVBH）.It was suggested that serious wear position of CVBH should be located at an interface between air and solid-liquid mixture within CVBH.Backfill slurry falls freely and impacts the wall of CVBH near the interface with great momentum and energy coming from high speed free fall of backfill slurry.The depth of serious wear position of CVBH,i.e.,free fall height of backfill slurry in CVBH,can be estimated by the height of vertical backfill drill-hole,the length of horizontal pipeline,the density of slurry and the hydraulic gradient of pipeline system.A case study indicated that the estimation equation of serious damage depth of CVBH was of enough accuracy and was helpful for daily maintenance and management of vertical backfill drill-hole.展开更多
Purpose:With the increasing level of automation in automobiles,the advent of autonomous vehicles hasreduced the tendency of drivers and passengers to focus on the task of driving.The increasing automation in automobil...Purpose:With the increasing level of automation in automobiles,the advent of autonomous vehicles hasreduced the tendency of drivers and passengers to focus on the task of driving.The increasing automation in automobiles reduced the drivers'and passengers'focus on driving,which allowed occupants tochoose a more relaxed and comfortable sitting position.Meanwhile,the occupant's sitting position wentfrom a frontal,upright position to a more relaxed and reclined one,which resulted in the existing restraint systems cannot to keep occupants safe and secure.This study aimed to determine the effects ofdifferent reclining states on occupants'lumbar and neck injuries.Methods:This is an original research on the field of automotive safety engineering.Occupants indifferent initial sitting positions(25°,35°,45°,and 55°)were adapted to changes in seat back angle andrestraint systems and placed in the same frontal impact environment.Neck injury indexes,lumbar axialcompression force and acceleration,as well as occupant dynamic response during the impact,werecompared in different sitting positions.The injury response and kinematic characteristics of occupants indifferent reclining positions were analyzed by the control variable method.Results:As the sitting angle increased,the occupant's head acceleration decreased,and the forward-leanangle decreased.Occupants in the standard sitting position had the greatest neck injury,with an Nij of0.95,and were susceptible to abbreviated injury scale 2+cervical medullary injuries.As the seatbackangle increased,the geometric position of the lumbar spine tended to be horizontal,and the impact loadtransmitted greater forces to the lumbar spine.The occupant's lumbar injury was greatest in the lyingposition,with a peak axial compression force on the lumbar region of 5.5 KN,which was 2.3 KN greaterthan in the standard sitting position.Conclusion:The study of occupant lumbar and neck injuries based on different recline states can providea theoretical basis for optimizing lumbar evaluation indexes,展开更多
基金Project (2008BAB32B03) supported by the National Key Technology Research and Development Program,China
文摘Vertical backfill drill-hole is usually a key project in an underground mine with backfill method and can be easily damaged by impact of backfill slurry.Observation of the damaged vertical backfill drill-holes in Jinchuan Nonferrous Metal Corporation（JNMC）,Gansu Province,China,given by a digital drill-hole video camera,indicated that there usually exist serious wear zones in casing pipe in vertical backfill drill-hole（CVBH）.It was suggested that serious wear position of CVBH should be located at an interface between air and solid-liquid mixture within CVBH.Backfill slurry falls freely and impacts the wall of CVBH near the interface with great momentum and energy coming from high speed free fall of backfill slurry.The depth of serious wear position of CVBH,i.e.,free fall height of backfill slurry in CVBH,can be estimated by the height of vertical backfill drill-hole,the length of horizontal pipeline,the density of slurry and the hydraulic gradient of pipeline system.A case study indicated that the estimation equation of serious damage depth of CVBH was of enough accuracy and was helpful for daily maintenance and management of vertical backfill drill-hole.
基金This study was supported by the National Natural ScienceFoundation of China(52175084 and 52175085)the NaturalScience Foundation of Hebei Province(E2020202017).
文摘Purpose:With the increasing level of automation in automobiles,the advent of autonomous vehicles hasreduced the tendency of drivers and passengers to focus on the task of driving.The increasing automation in automobiles reduced the drivers'and passengers'focus on driving,which allowed occupants tochoose a more relaxed and comfortable sitting position.Meanwhile,the occupant's sitting position wentfrom a frontal,upright position to a more relaxed and reclined one,which resulted in the existing restraint systems cannot to keep occupants safe and secure.This study aimed to determine the effects ofdifferent reclining states on occupants'lumbar and neck injuries.Methods:This is an original research on the field of automotive safety engineering.Occupants indifferent initial sitting positions(25°,35°,45°,and 55°)were adapted to changes in seat back angle andrestraint systems and placed in the same frontal impact environment.Neck injury indexes,lumbar axialcompression force and acceleration,as well as occupant dynamic response during the impact,werecompared in different sitting positions.The injury response and kinematic characteristics of occupants indifferent reclining positions were analyzed by the control variable method.Results:As the sitting angle increased,the occupant's head acceleration decreased,and the forward-leanangle decreased.Occupants in the standard sitting position had the greatest neck injury,with an Nij of0.95,and were susceptible to abbreviated injury scale 2+cervical medullary injuries.As the seatbackangle increased,the geometric position of the lumbar spine tended to be horizontal,and the impact loadtransmitted greater forces to the lumbar spine.The occupant's lumbar injury was greatest in the lyingposition,with a peak axial compression force on the lumbar region of 5.5 KN,which was 2.3 KN greaterthan in the standard sitting position.Conclusion:The study of occupant lumbar and neck injuries based on different recline states can providea theoretical basis for optimizing lumbar evaluation indexes,
