| A lot of high dams have been built around the world. According to incomplete statistical data, there are 28 dams more than 200m high and 6 dams more than 250m among of them. China is the country of having the most dams around the world. Until 1997, 21 thousand dams of more than 15m high have been built. 12 dams of more than 150m high have been built or being built. Construction of some super high dams, such as Ertan hydropower station with 240m high dam, greatly promotes the technology of large hydropower station construction. As we know, most of the dams are successful and they provide us lots of useful experience. However, it is also necessary to summarize lessons from destroyed dams due to various reasons.Thermal load in arch dam is only inferior to water pressure in arch-dam design. At the boundary of the upstream reservoir, the rationality and precision of water temperature analysis is very important to consider the deformational behavior of dams. To design the hydraulic structure, reservoir water temperature is calculated by empirical models and heat balance method. For example, average annual water temperature and annual variation are calculated by heat balance theory. However, there may be some error or limit in the result. The models usually adopted to analyze the reservoir water temperature are based on statistical results. Those models can be applied to dams of 100m high level only. When we apply the currently used methods to practical projects with dams of 200m high, such as Ertan, Xiaowan, Xiluodu, Laxiwa, Jinping hydropower stations, the predicted temperature of upstream water is obviously different from the measured. Water temperature in reservoir is relative to background characteristics (air temperature, natural water temperature, discharge, sediment discharge, hot radiation and ground temperature, etc.) and reservoir characteristics (regulating function, discharging way and sediment deposition, etc.). The theoretical calculation of water temperature cannot take all the complicated factors into account. Therefore, predicting methods and formula are still need to study further at present.Measured time series of water temperature near upstream during 6 years are used for analysis and calculating water temperature distribution pattern. The data is transformed into thermal load and is used for back analysis of stress and strain for arch dam.The main research contents are as follows: (1) Study on the distribution pattern of water temperature near dam in design phrase. (2) The calculation of the measured water temperature in front of the dam. (3) Comparison of the data coming from thermometer with the data coming from temperature pickup. (4) Collection and analysis of measured water temperature 300m far from the dam. (5) Analysis and comparison of the data, which is got from calculation by experience formula and measure. (6) The influence of water temperature variation on thermal load on dam body.The paper has gained some valuable achievement based on practice engineering, and given the computational formula of average annual water temperature and average annual transformation rate, as well as water temperature distribution pattern near dam with high arch dam and large reservoir capacity and the difference of production from empirical formula using regression analysis for the surveyed data in 6 years, which is gathered by thermometer and some instruments. All of these contribute to safety evaluation and normal operation for Ertan arch dam.Until now, Ertan is only the 200m high arch dam of being under operation. A lot of high dams are under being designed or built in our country. So the analysis for monitored data of reservoir water close to dam not only provides a lot of referential material for other arch dams, but also plays a monitoring role in operation safety of Ertan arch dam. |
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