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1、 The Three Gorges Project approach channel flow of a reasonable size of Flushing Abstract: This paper a systematic comparison of the Three Gorges Project and Gezhouba project specific conditions, combined with sediment physical and mathematical models of research and put forward the Three Gorges cha
2、nnel quoted a reasonable size Flushing flows. The Three Gorges Project can be smaller than the Gezhouba project “small flow safari” measures to achieve “water will move sand.” Under normal conditions, the approach channel safari size of the facility control 4000m3 / s within the range, we can achiev
3、e very good results Flushing; if safari to give further consideration to reduce reservoir water level of small magnitude, it still can be further reduced safari Flushing flow or increase the effect. Scouring the Department of lowering the water level of non-structural measures, could serve as a futu
4、re in the use of margin of safety. This paper suggests, the Three Gorges Project with 4000m3 / s the size of the sand-flushing flow. Keywords: Three Gorges Project approach channel silt sand small flow of water will move 1 Introduction Three Gorges Project is to improve the navigation conditions in
5、the upper reaches of the Yangtze River shipping conditions of the key. To this end, the Three Gorges Project layout of the two-five-sets navigation lock and the vertical ship lift construction, so that navigation Gezhouba project size and the same three-wire locks. According to Gezhouba project expe
6、rience and the Three Gorges project sediment research 1 4, in the engineering application of the latter part of the dam area of the sediment deposition would be more serious approach channel upstream and downstream silting arrangement of a certain length of separation levee is necessary to The. To t
7、his end the Three Gorges downstream approach channel with a long separation levee would be quoted separately from the mainstream channel, the upstream approach channel will be used to build a lock, ship lift the temporary ship lock approach channel, and converted by the flushing sluice include all t
8、he so-called “ the whole package “separation levee program. As the temporary ship lock of the gap can be converted to be able to discharge 2500m3 / s of flushing sluice, so “full package” program has provided an important safari safari facilities. While anti-down approach channel to build a sludge s
9、eparation levee, but the upper and lower approach channel is still a great amount of sediment deposition during the year. According to research statistics, to the latter part of the upstream and downstream approach channel of the navigation-deposition volume in more than 1 million m3. Navigation con
10、ditions, taking into account the limitations and deposition non-uniformity in time alone would be difficult to cope with mechanical dredging, and must take into account a certain amount of water safari facilities. Gezhouba project a “hydrostatic off ships, moving water will sand” 7 has been proven s
11、uccessful experience in the Three Gorges Project should learn from. However, the Three Gorges and Gezhouba project there is any difference, the Three Gorges Project can make use of Gezhouba project does not have favorable conditions, instead of copying the size of the Gezhouba the safari. Three Gorg
12、es “moving water will sand” scale should be based on their specific situation analysis to decide. According to the author in recent years, the Three Gorges Project on the upstream and downstream approach channel sedimentation countermeasures physical model test and mathematical model study, a detail
13、ed analysis of the Three Gorges Project on the basis of favorable conditions proposed in this paper can be “small flow safari” measures to achieve the Three Gorges project, “moving water will sand”, citing the size of channel sand-flushing facilities, control the 4000m3 / s within the range, we can
14、achieve very good results safari. If we further consider lowering the reservoir water level and other non-structural measures, safari flow can also be reduced, which can serve as a room will help to ensure the smooth flow of the Three Gorges down approach channel. 2 Gezhouba Engineering and Comparis
15、on of the Three Gorges project safari conditions Gezhouba project to move water will sand approach to the maintenance of upstream and downstream approach channel has played a decisive role, it is worthy of the Three Gorges Project reference. However, due to the Three Gorges and Gezhouba project, aft
16、er all, there are differences, quantitative decided that the scale of the Three Gorges Project Flushing flows should be read with the Three Gorges Project to conduct a concrete analysis of specific conditions. Zhang Ruijin the analysis of the situation and Gezhouba project concludes that “hydrostati
17、c off ships, moving water will sand” measures are based on the following three objective conditions 7, namely: 1) The annual average sediment concentration in the Yangtze River are slightly greater than 1kg/m3 the “river of sand”; 2) Gezhouba project is abundant water run-off-type power plants each
18、year for a long time there are more abandoned water; 3) Hub outlet sluice flood need more, flushing sluice sluice can play a role. Comparison of the Three Gorges Project and Gezhouba project, in terms of there is a big difference. These differences are due to project size, head and upper reaches of
19、the Yangtze River flood as well as the layout of large hydropower projects by the combined effect of group decision. Three Gorges Project and Gezhouba project, although only a few dozen kilometers away from the natural conditions, water conditions, sand is almost exactly the same. However, the Three
20、 Gorges Project is a multi-billion m3 storage capacity, allowing the 10 billion m3 of sediment deposition in large reservoirs, although the initial reservoir operation is also a considerable number of sand reach the dam, but the reservoir to be around 100 130 years to reach an initial The erosion an
21、d deposition balance, balance of the sediment before the dam to reach the concentration will be far less than the natural situation, at least the first 30 years of siltation will not be cited as the Gezhouba project channel as serious. Meanwhile, the countries have listed on the agenda the developme
22、nt of the Jinsha River, Xiangjiaba, or one of the river off the ferry is expected to start in 10 years. Even a relatively small storage capacity Xiangjiaba Reservoir, the first 30 years the average annual sediment volume estimates also reached 125 million m3 8, the Yangtze River is about a quarter o
23、f the total amount of sediment. The upstream reservoir sediment, the Three Gorges project from top to bottom approach channel in the short and long-term sediment deposition will be a certain delay. The construction of large-scale but only after decades of use safari facilities is bound to create a g
24、reat backlog of funds. Three Gorges Project is not a run-of-power station. Three Gorges Project water level in the 145m, the plants need full-fat flow of about 22000m3 / s, need safari in September of each year when the Yangtze River to flow an average of only 27500m3 / s, although there are some ab
25、andoned water, but water is already abandoned small. In particular, the upstream reservoir, once operational, comprehensive utilization of water resources and optimizing the scheduling more will greatly reduce disposable water, the Three Gorges project. In abandoning the hub of a smaller amount of w
26、ater used for safari amount of water must pass a comprehensive economic comparison to be reasonably determined. Flushing flow if too large, the timing of safari can be arranged each year will be limited, shipping and power generation will highlight the contradiction. The Three Gorges Project is the
27、hub of high-head. It includes a large-scale flood the building. Safari facilities as Gezhouba project is no longer necessary, as is a flood one of the facilities, their construction investment, we must seriously consider. Moreover, if the size of the facility as the safari as Gezhouba project, to 80
28、00 10000m3 / s of traffic, then due to head high, tunnel layout, energy dissipation, etc. will have great difficulty, especially in tunnel construction and over-current high slope of the lock stability and security implications may be significant. Set the feasibility of large-scale sand-flushing tun
29、nel need to study carefully. Three Gorges Project ship lock and the ship lift will be two sets of navigation facilities are arranged on the left, right part of the approach channel of the common use and navigation management, and bring some benefits, but the flight paths of the siltation and flow co
30、ntrol is brought back and forth to the difficulties 5,6, especially in the upstream approach channel of the safari, regardless of the Three Gorges Project with which separation levee layout program, using much of the safari flow approach channel will exist in both safaris “dead zone”, Mechanical dre
31、dging as a supplementary measure to clear the corners and other dead zone of sediment deposition is necessary. Approach channel safari can only solve the problem of silting the main channel line. Reposted elsewhere in the paper for free download The feasibility of small flow safari 3 The Three Gorge
32、s Project to control the upstream approach channel width (139m elevation above the average 240m) than the Gezhouba project Sanjiang upstream approach channel of minimum width (57m above the average elevation 250m) is slightly narrower, while the safari when the channel depth varied widely. The Three
33、 Gorges Project water level in flood season is to limit water level 145m, approach channel safari is only when the maximum depth 6m; Gezhouba project as the Three Gorges Project, anti-regulation reservoirs, the design requirements it has a 3m water level amplitude, the corresponding water level is 6
34、6 63m, safari when the water level is generally 66m or 66.5m (1987 years), according to the same requirements of depth, the largest safari Gezhouba project depth of 9m. Figure 1 is a 1995 safari around the Gezhouba Sanjiang approach channel cross-section of the entrance. After the safari over the wa
35、ter area of 2781m2, average water depth of up to 11m, more than the previous use of the 9m. The Three Gorges Project on the approach channel depth of the safari Gezhouba smaller than 1 / 3. Assuming that the beginning of channel silting Scouring the same as the thickness of 2m, then the Three Gorges
36、 channel of the water depth is only a more Gezhouba 4 / 7. Zhang Ruijins sediment-carrying capacity according to the formula Figure 1 Gezhouba Sanjiang on the approach channel entrance cross section before and after the safari Measured inlet sections in Sanjiang upper approach of Gezhouba Project be
37、fore / after flushing S = k (u3/ghw) (1) Where U is the average velocity; h is the depth; is the sediment settling velocity; g = 9.81; m 1.0. As the Three Gorges and the Gezhouba only a few dozen kilometers away from the Three Gorges approach channel of silt and sediment Gezhouba approach channel sh
38、ould be very close, basically the same velocity. Flushing in the same flow rate, the Three Gorges approach channel, the average velocity is 1.56 1.82 times the Gezhouba, therefore, the Three Gorges approach channel of the sediment carrying capacity will be Gezhouba 5 10 times. On the upstream approa
39、ch channel, the Three Gorges project apparently did not need to use the same safari with the Gezhouba project flow. If the Three Gorges and Gezhouba channel upstream of the sediment carrying capacity by the same design, by the formula (1) the Three Gorges Project approach channel of the safari flow
40、Q Three Gorges safari = (0.44-0.54) Q Gezhouba Sanjiang safari (2) Flushing flow channel Gezhouba Sanjiang generally 8000m3 / s, therefore, the Three Gorges channel of the safari upstream flow of approximately 4000m3 / s. The Three Gorges Project water level in the downstream approach channel throug
41、h the Gezhouba project control, safari can be reduced. Three Gorges downstream approach channel with a width of 180m, I gate width 200m, at the end of the maintenance of channel height for the 57m, the minimum water level in flood season is controlled by the Gezhouba Reservoir 66m (about 67 69m), th
42、e year the minimum navigable level of 63m; Gezhouba three rivers downstream The minimum channel width of 120m, exit door width is 150m, channel elevation of the end of the maintenance of 34.5m, the year the minimum navigable level of 39.0m. In contrast, the downstream approach channel Gezhouba proje
43、ct should be better than the Three Gorges of the cross-sectional area under the approach channel is small, sand-flushing conditions, should be more favorable than the Three Gorges Project. However, because Gezhouba project is run-of-power plants, the timing could not arrange safari fairways dry seas
44、on river flow is greater than normally required in the 22000 23000m3 / s when the safari, this time, the downstream river water is higher than 46.5m , the largest sand-flushing water depth is greater than 12.0m. The water level downstream of the Three Gorges Project is in control of the reservoir Ge
45、zhouba project within the scope of flood at the end could be to consider lowering the reservoir water level Gezhouba safari. Scouring the proposed Three Gorges dam when the reservoir water level Gezhouba reduced to 62.5m, the Three Gorges Project water level of exports under the approach channel wil
46、l be 63 63.5m, maximum depth of about Flushing 6.5m. Safari when the maximum water depth of the Three Gorges Project Gezhouba project 54.2%; assumption safari begins, the Three Gorges Project and the deposition thickness of both Gezhouba project 2m, then the depth of the Three Gorges Project is only
47、 45% of Gezhouba project. Scouring over the water when the Three Gorges area of the largest of only Gezhouba 58.4 71.1%; in the same flow rate, the Three Gorges Project downstream approach channel of the sediment carrying capacity is the Gezhouba project 5 11 times. If the sediment carrying capacity
48、 by the same design, then the Three Gorges project the size of the downstream flow of Flushing Q Three Gorges safari = (0.45-0.58) Q Gezhouba Sanjiang safari (3) And (2) basically the same. On the other hand, the same formula (1) sediment carrying capacity as measured by, safari, when the Three Gorges Project downstream approach channel will be higher than th