土石壩外文翻譯---土石壩及溢洪道設計-其他專業(yè)-文庫吧資料
2025-01-27 08:34本頁面
【正文】 safety. In the first aspect, the flow is studied for periods of drought and programmed into this study. A mass curve of the stream runoff over a period of years is developed to determine the available water. The mass curve is the accumulative total of the volume of flow past a given point on the stream over a period of time. Unfortunately, most of the small streams do not have sufficient records to develop the hydrologic information. The engineer usually develops synthetic curves from neighboring stream data and rainfall information. However, methods are available in various texts, journals, and reports to estimate stream flow. The second aspect involves estimating maximum flood flow to determine spillway requirement and dam safety. Studies show that flood flows are associated with frequency of the event of the risk of floods causing damage by exceeding the estimated design flow. If failure of the dam would result in loss of life, the spillway must have sufficient capacity to prevent failure when the maximum probable flood is routed through the reservoir. This is particularly important in rock and earthfill dam that may be overtopped during a flood. Concrete dams can generally withstand some overtopping without failure if the structural analysis adheres to the generally accepted safety factors. The case of dam failure that does not endanger life may be justified if the anization involved fully realizes the risks and ensuing damages. This situation may exist on low, small reservoirtype dams. A quick estimates of maximum probable flow can be obtained from a figure. Discharge determined from these curves should be modified by application of hydrologic data pertinent to the area. The curves are based records of unusual flood discharges for unregulated streams. The engineer should not accept the flood peak established from these experience curves without first bringing the data up to date to show all recent flood events and those pertinent to the area of study. An advanced procedure to estimate the maximum flood is to transpose storm producing great floods in the region over the drainage basin. The resulting flood is analyzed to determine the peak flow and the hydrograph. The hydrograph is the relationship of discharge and time for precipitation when bined with other floodcontributing of the basin (including melting snow)to produce the flood hydrograph. Flood less than maximum may be used for structures where loss of human life is not involved. In minor structures with insignificant storage, where it is permissible to anticipate failure within the useful life of the project, a 50year or 100year frequency flood may be used for the inflow design flood. Site conditions greatly influence the location, type, and ponents of the spillway. The type of dam construction is also influenced by the type of spillway and spillway requirements. There are six general categories of spillways: ① overflow ,② through or chute, ③ side channel, ④ shaft or glory hole, ⑤ siphon, ⑥ gated. The designer may use one or a bination of types to fulfill the project needs.
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