Study On Failure Mechanism Of New Type Of Ecological Revetment Structure

The reef bank protection structure is a kind of new ecological revetment structure applied in the middle and lower reaches of Yangtze river.The structure enriches the revetment structure type and improves the ecological function of revetment structure.The ability of the new structure under the action of water and sediment to resist damage is no research.So the study on the structure failure mechanism has important practical significance.In this paper,it solves problems related with designing reefs ecological revetment structure with the method of numerical simulation,experimental study in the sink and fuzzy comprehensive evaluation.And what it focuses on is the failure mechanism of the revetment structure.The following is the main conclusions of this paper.(1)It puts forward two types of the ecological revetment structure used fish reef.And the paper expounds the connotation of the new structure.The structure combines the advantages of the artificial fishing reef engineering and the bank protection structure,enriches the structure of bank protection structure,improves the ecological function of ecological revetment structure;(2)It simulates the water flow with single block and different inlet velocity,0.8 m/s as a condition of ceiling,to design the spacing of reef blocks.The design of the reefs block spacing reduces the project cost as far as possible under the premise of meeting the ecological requirement.It achieves the best balance between ecological and economic.In the end,it is proved that 6 m and 3.64 m is the most reasonable as nut reefs blocks and diamond reefs blocks spacing;(3)It reveals the destruction mechanism of the new structures through movable bed physical model test.The damage phenomenon are two main aspects:? The Fluid erosion to slope toe,causes a downturn of the common the block at the bottom of the structure.And then it causes the overall destruction;? Under the condition of low water depth,in the structure of the upstream,the impact of the water leads to the local failure of structure with a triangular incision.The shear stress near block the is larger;the sediment near blocks is easier to start;block will lose focus and decline.This is the root cause of new bank protection structure damage.(4)With the analysis of Kcq stability coefficient formula,the reason that the diamond and nut showed different displacement in the form of a block in the experiment was that anti-inclining lever of the diamond blocks is less than nut blocks.(5)The phenomenon that the blocks cover for each other in the test was observed.But the phenomenon of diamond blocks is not obvious.It analyzed the phenomenon based on the test.wake zone appears after the front blocks,changes the flow structure and makes the downstream blocks protected by upstream blocks.The cover phenomenon of diamond blocks is not obvious mainly caused by the difference of the hollow ratio and projection area A;(6)Analysis of relationship of the structure of the extent of damage and flow velocity:displacement increased with increasing of flow velocity;there is also positive correlation between incision area and flow velocity;(7)By comprehensive compared different damage phenomenon of two type structure,it is concluded that the stability of nut block is better than diamond blocks under the action of water and sediment under the condition of no protective measures;(8)Though the method of fuzzy comprehensive evaluation,it is concluded that two fish reef bank protection structure are better than traditional revetment structure;there is little difference between the two types of fish reef revetment structure.