The settling behavior of coarse particles in a gas-solid fluidized bed was experimentally studied by using magnetic tracer. It is well known that the calculation of terminal velocity is of interest in dense medium sep...The settling behavior of coarse particles in a gas-solid fluidized bed was experimentally studied by using magnetic tracer. It is well known that the calculation of terminal velocity is of interest in dense medium separation. However, this problem has not been completely solved up to now. In this work, the terminal velocity of an object mov-ing in a gas-solid fluidized bed was experimentally measured and theoretically calculated. The experimental results in-dicated that the plastic viscosity and yield stress of the bed increase as the size of fluidized particles increases, but it varies little when some coarser particles are mixed with the fluidized particles. The resistance to a rising object was an order magnitude greater than that to a settling object. The efficient buoyancy on a flaky object, which lies flatly on the gas distributor, was much less than that calculated by the Archimedes principle. The object does not always rise or set-tle with minimal projective area owing to radial motion of the fluidized particles. But in the lower part of the bed, the bar-shaped objects were likely with minimal projective area rising or settling.展开更多
Since different underground engineering contains different geological conditions,structure and excavation methods,their disturbing degree on the ground also differs,but ground surface settlement caused by excavation h...Since different underground engineering contains different geological conditions,structure and excavation methods,their disturbing degree on the ground also differs,but ground surface settlement caused by excavation has one common point that they will form a ground surface settlement curve.Based on data statistical analysis,the article puts forward the relationship between point of inflection in digging tunnels with shallowburied method and the span of tunnel excavation against typical geological conditions in Changchun so as to predict the impact of tunnel excavation and improve reasonable ground surface settlement control standard.Research result will be useful for study on ground surface control standard in digging tunnels with shallow-buried method and setting settlement standard.展开更多
Now the surface settlement induced by shallow buried tunnel to under-traverse highway,mostly adopt the empirical value,3 cm,acquired from Beijing or Shenzhen metro,which is regarded as the controlling standard.But to ...Now the surface settlement induced by shallow buried tunnel to under-traverse highway,mostly adopt the empirical value,3 cm,acquired from Beijing or Shenzhen metro,which is regarded as the controlling standard.But to more project,tunnel under-traverse highway,we must decide the controlling standard flexibly,which should base on the pavement service function and the pavement condition.The thesis,based on the pavement evenness and running comfort ability in the view of completing the pavement service function,supposes the longitudinal pavement settlement cross section as a quadratic parabola,and gets the maximal settlement value in the range of longitudinal pavement influence when the tunnel is under-traverse highway perpendicularly.Then the controlling standard is decided.As Wenxiang Tunnel under-traverse Lianhuo Freeway on Zhengzhou-Xi'an Passenger Dedicated Railway Line for an example,the settlement controlling standard is acquired,and we hope it has an direction and reference value to similar tunnel construction.展开更多
基金Projects (504740309021003550025411) supported by National Natural Science Foundation of China
文摘The settling behavior of coarse particles in a gas-solid fluidized bed was experimentally studied by using magnetic tracer. It is well known that the calculation of terminal velocity is of interest in dense medium separation. However, this problem has not been completely solved up to now. In this work, the terminal velocity of an object mov-ing in a gas-solid fluidized bed was experimentally measured and theoretically calculated. The experimental results in-dicated that the plastic viscosity and yield stress of the bed increase as the size of fluidized particles increases, but it varies little when some coarser particles are mixed with the fluidized particles. The resistance to a rising object was an order magnitude greater than that to a settling object. The efficient buoyancy on a flaky object, which lies flatly on the gas distributor, was much less than that calculated by the Archimedes principle. The object does not always rise or set-tle with minimal projective area owing to radial motion of the fluidized particles. But in the lower part of the bed, the bar-shaped objects were likely with minimal projective area rising or settling.
文摘Since different underground engineering contains different geological conditions,structure and excavation methods,their disturbing degree on the ground also differs,but ground surface settlement caused by excavation has one common point that they will form a ground surface settlement curve.Based on data statistical analysis,the article puts forward the relationship between point of inflection in digging tunnels with shallowburied method and the span of tunnel excavation against typical geological conditions in Changchun so as to predict the impact of tunnel excavation and improve reasonable ground surface settlement control standard.Research result will be useful for study on ground surface control standard in digging tunnels with shallow-buried method and setting settlement standard.
文摘Now the surface settlement induced by shallow buried tunnel to under-traverse highway,mostly adopt the empirical value,3 cm,acquired from Beijing or Shenzhen metro,which is regarded as the controlling standard.But to more project,tunnel under-traverse highway,we must decide the controlling standard flexibly,which should base on the pavement service function and the pavement condition.The thesis,based on the pavement evenness and running comfort ability in the view of completing the pavement service function,supposes the longitudinal pavement settlement cross section as a quadratic parabola,and gets the maximal settlement value in the range of longitudinal pavement influence when the tunnel is under-traverse highway perpendicularly.Then the controlling standard is decided.As Wenxiang Tunnel under-traverse Lianhuo Freeway on Zhengzhou-Xi'an Passenger Dedicated Railway Line for an example,the settlement controlling standard is acquired,and we hope it has an direction and reference value to similar tunnel construction.
