Study On Measures To Improve The Navigation Condition Of Typical Segment Under Large Discharge Between The Three George And The Gezhouba Reservoir

Based on the analyses of extensive data collected from the related project and domestic and oversea research results, the combined methods of field investigation, data analysis, and physical model tests were applied to investigate the navigation safety under large discharge between the Three George and the Gezhouba Reservoir. Following main results were obtained.(1)The river channel presents characteristics of gorge type shape between the Three George and the Gezhouba Reservoir. In flood period, the increase speed of the discharge area is smaller than that of the discharge. The rapid flow and disorder flow pattern are apparent characteristics for navigation-obstructing due to rapids and shoals, and the basic reasons are the plane, cross-section and longitudinal profiles. So the total principle for the channel regulation is to adjust flow structure and velocity distribution through changing riverbed shape so that bad navigation-obstructing flow pattern is eliminated or weakened.(2)The velocity, gradient, backflow scope increase with the discharge. The width of main flow increases with the discharge, and decreases with the water level of the Gezhouba Reservoir.(3)The results of physical model test on regulation measures for ShiPai bend show that the main velocity area was widened and the circumfluence was compressed, the discharge in the surface layer of kolk boil area increases, the effective flow area grows and the velocity tend towards uniform. The appearance frequency of kolk boil decreases and the strength weakened. The flow condition is improved obviously.(4)The results of physical model test on non-engineering measures for improving navigation condition present that the rapid flow width decreases with the water level rise above the Gezhouza Reservoir, which can improve the flow condition and provides better navigation condition.