Bridge pressure flow scour at clear water threshold condition is studied theoretically and experimentally.The flume experiments reveal that the measured scour profiles under a bridge are more or less 2-dimensional;all...Bridge pressure flow scour at clear water threshold condition is studied theoretically and experimentally.The flume experiments reveal that the measured scour profiles under a bridge are more or less 2-dimensional;all the measured scour profiles can be described by two similarity equations,where the horizontal distance is scaled by the deck width while the local scour by the maximum scour depth;the maximum scour position is located just under the bridge about 15% deck width from the downstream deck edge;the scour begins at about one deck width upstream the bridge while the deposition occurs at about 2.5 deck widths downstream the bridge;and the maximum scour depth decreases with increas-ing sediment size,but increases with deck inundation.The theoretical analysis shows that:bridge scour can be divided into three cases,i.e.downstream unsubmerged,partially submerged,and totally submerged.For downstream unsubmerged flows,the maximum bridge scour depth is an open-channel problem where the conventional methods in terms of critical velocity or bed shear stress can be applied;for partially and totally submerged flows,the equilibrium maximum scour depth can be described by a scour and an inundation similarity number,which has been confirmed by experiments with two decks and two sediment sizes.For application,a design and field evaluation procedure with examples is presented,including the maximum scour depth and scour profile.展开更多
Fracking is one of the kernel technologies in the remarkable shale gas revolution. The extended finite element method is used in this paper to numerically investigate the interaction between hydraulic and natural frac...Fracking is one of the kernel technologies in the remarkable shale gas revolution. The extended finite element method is used in this paper to numerically investigate the interaction between hydraulic and natural fractures, which is an important issue of the enigmatic fracture network formation in fracking. The criteria which control the opening of natural fracture and crossing of hydraulic fracture are tentatively presented. Influence factors on the interaction process are systematically analyzed, which include the approach angle, anisotropy of in-situ stress and fluid pressure profile.展开更多
文摘Bridge pressure flow scour at clear water threshold condition is studied theoretically and experimentally.The flume experiments reveal that the measured scour profiles under a bridge are more or less 2-dimensional;all the measured scour profiles can be described by two similarity equations,where the horizontal distance is scaled by the deck width while the local scour by the maximum scour depth;the maximum scour position is located just under the bridge about 15% deck width from the downstream deck edge;the scour begins at about one deck width upstream the bridge while the deposition occurs at about 2.5 deck widths downstream the bridge;and the maximum scour depth decreases with increas-ing sediment size,but increases with deck inundation.The theoretical analysis shows that:bridge scour can be divided into three cases,i.e.downstream unsubmerged,partially submerged,and totally submerged.For downstream unsubmerged flows,the maximum bridge scour depth is an open-channel problem where the conventional methods in terms of critical velocity or bed shear stress can be applied;for partially and totally submerged flows,the equilibrium maximum scour depth can be described by a scour and an inundation similarity number,which has been confirmed by experiments with two decks and two sediment sizes.For application,a design and field evaluation procedure with examples is presented,including the maximum scour depth and scour profile.
基金supported by the National Natural Science Foundation of China (Grant No. 11372157)the Special Research Grant for Doctor Discipline by Ministry of Education of China (Grant No. 20120002110075)the Foundation for the Author of National Excellent Doctoral Dissertation of China (FANEDD) (Grant No. 201326)
文摘Fracking is one of the kernel technologies in the remarkable shale gas revolution. The extended finite element method is used in this paper to numerically investigate the interaction between hydraulic and natural fractures, which is an important issue of the enigmatic fracture network formation in fracking. The criteria which control the opening of natural fracture and crossing of hydraulic fracture are tentatively presented. Influence factors on the interaction process are systematically analyzed, which include the approach angle, anisotropy of in-situ stress and fluid pressure profile.
