Technical Research On The Regulation Of Bending Braided Shoals In Mountain River

The bending braided shoals which mainly blocked the waterway, are widely existed in moutain rivers. The basic factors of regulating bending braided shoals are water and sediment movement characteristics,stream features of digging channels and influence on sediment movement caused by different section of digging channels. Worldwide geophysicists have made a lot of studies on this project, but until recently the research which can reflect water and sediment movement characteristics and digging steability features has been less fruitful.So research on regulation of mountain river bending braided shoals is important and valuable in theoretical and engineering fileds.This paper collected the corresponding research materials from home and abroad and the typical regulation case of Tonggutan.By theoretical analyzing and model experiment, this paper researched on the movement characteristics of water and sand, steability of different digging sections and measurements of curved shoal in the filed of bending braided shoals.Firstly, when widening rateβ=1, this paper obtained that widening rate is gradually increasing from to the bent channel by theoretical analyzing .It reaches a maximum in the bend sections and then drops down along the channel.When the number ofβis larger,the max widening rate will occur in the entrance and the bend section.Secondly, combine with the digging results of Tonggutan, when aspect ratio B/H=17.8～21.5 of digging section,it has larger intensity about sediment transport and the new navigable channel is better to use the narrow deeping form by analyzing the steam features of digging channel and the effects to sediment movement caused by digging section's forms.Thirdly, the physical model researchs on Tonggutan show that it's better to use the low water measurement with capital construction dredge up and damming together for digging new channels in bending braided shoals. It can increase distribute rate and gravel motion power by building the longitudinal dike and moraine in river centre and building ground sills and groyne in bent channel as well as dredging. building dams will bunch water in order to maintain avigable channels'steability. Finally, the results about steability research show that under the complex conditions of mountain river, the proper speed for digging channel is 1.1～1.3V.The incipient velocity formula take velocity formula Cuntan index and the grain diameter take median size D50 of the natural sand.