A Study On The Conditions For Enabling The Special Spillway Of Luhun Reservoir Based On The Risk Of Flood Control Operation

As a large(Ⅰ) reservoir in the middle and lower reaches of the Yellow River,Luhun Reservoir has a significant impact on the development of cities in the area.The extraordinary spillway,that is,an unconventional discharge structure,functions to reduce the risk of reservoir operation when the reservoir encounters a catastrophic flood.Therefore,a reasonable activation of extraordinary spillway can effectively discharge the flood to ensure the safety of the reservoir.Based on the preliminary study and hydraulic model test of the extraordinary spillway of Luhun Reservoir,this paper furthers the study of the conditions for the activation of extraordinary spillway.Owing to few studies on the application of extraordinary spillways,this thesis first clarifies the general idea of extraordinary spillway research during the research process,and then combines risky factors with Luhun reservoir’s operation process based on risk analysis principles so as to determine an acceptable flood process.The water level in front of the dam of the extraordinary spillway is analyzed and calculated in accordance with the acceptable flood process in combination with the flood regulation of Luhun Reservoir.The main work and research results are as follows:(1)The scenario of extraordinary spillway opening is accurately confirmed according to the dispatching characteristics and design standards of Luhun Reservoir during flood and non-flood seasons.Due to the complicated scenario of the extraordinary spillway,the initial water level is set to 317.5m and 319.5m in the research process of this paper;the flood standard is: the 10,000-year flood process,the over-standard flood process,the initial water level and the flood standard are combined Way to complete the scene setting of the extraordinary spillway activation.The purpose of adopting this scenario setting is to relatively and comprehensively consider the activation conditions of the extraordinary spillway when Luhun Reservoir encounters different standard floods during the flood and non-flood seasons,thus laying the foundation for the following research.(2)According to the dispatching rules of Luhun Reservoir,the water level in front of the dam of the extraordinary spillway is determined as the indicator of the extraordinary spillway in the circumstance of combining with the dispatching situation of the reservoirs at different water levels.In the research process of thispaper,the importance of flood control of Luhun Reservoir is taken into consideration.On the basis of the regulation of Luhun Reservoir,it is ensured that the extraordinary spillway can be activated in time when the reservoir encounters a catastrophic flood.The water level in front of the dam is used as an index for activation.(3)In view of the dispatching risks of reservoir,the mode of Monte Carlo simulation coupling with the reservoir regulation is used to successfully couple the flood process with four risky factors: discharge capacity,water level-reservoir capacity,dispatching delay time and primary regulating water level so as to determine the flood process acceptable to the risk of flood control operation.The risk rate is calculated by the coupling method of Monte Carlo simulation and flood regulation of Luhun reservoir based on the functional relationship between the risk objective and the selected risk factors.The inflow peak discharge which meets the risk rate requirements is determined in combination with the risk critical value.The correlation relationship between peak volumes and the acceptable flood process are confirmed on the basis of the data of natural annual maximum peak discharge,maximum 1-day flood volume,3-day flood volume and 5-day flood volume of Luhun station in 1943 and 1951-2012.It paves the way for the calculation of the water level in front of the dam of unconventional spillway in the following text.(4)The flood regulation calculation of Luhun Reservoir was carried out in combination with the acceptable flood process,the water level before the opening of the extraordinary spillway was determined,and the scientificity of the water level before the opening of the extraordinary spillway was verified.The 10,000-year flood process:(1)The starting water level is 317.5m,and the water level in front of the dam has a rising trend of more than 328.18 m.Consider opening the extraordinary spillway,and the highest water level in front of the dam can be controlled below 328.74m;(2)The starting water level is 319.5m,in front of the dam If the water level exceeds327.45 m,the upward trend is obvious.Consider opening an extraordinary spillway,and the highest water level in front of the dam can be controlled below 328.26 m.Exceeding standard flood process:(1)The starting water level is 317.5m,and the water level in front of the dam is over 330.80 m.The rising trend is obvious.Consider opening an extraordinary spillway,and the highest water level in front of the dam can be controlled below 331.10m;(2)The starting water level is 319.5m,and the water level in front of the dam exceeds The rising trend of 330.43 m is obvious,and the extraordinary spillway should be considered to control the highest water level in frontof the dam below 330.70 m.