Author(s): Yuanfeng Zhang; Tianjun Hu
Linked Author(s):
Keywords: Yellow River; Ripping up bottom scour; Critical condition; Loss stability of gummy bar; Principle of minimum potential energy
Abstract: The phenomenon of Ripping up bottom scour often occurs during hyper-concentrated flood period and intensive scour of the river bed is rapidly caused in the Middle Yellow River. Based on deposit layer characteristics, the concept of elastic gummy layer for the river bed is proposed and the gummy bar for unit width of river bed along the flow direction is regarded as a compress column. With the method of sections of material mechanics and the principle of minimum potential energy, i. e. Rayleigh Ritz method, critical forces for loss stability of gummy bar are calculated. Then the critical conditions for loss stability of the compress column and rotary equation of the bar which rolls up around its thickness center are obtained. According to the equation it can be described that the gummy bar will be lift up and accelerates its rolling along the river bed like reel shape as soon as the loss stability takes place. The gummy bar increases with the bending increasing. When the elastic stress limit has been exceeded the plastic deformation or fracture occurs. The broken part quickly accelerates rolling around the fixed axis until it throws or drops off. With the proposed formula in this paper, the calculated gummy layer thicknesses agree with the Middle Yellow River measurements during hyper-concentrated flow floods period when ripping up bottom scour occurred.
Year: 2013