【作者】 张颖；

【导师】 刘华； 孙炯；

【作者基本信息】 四川大学 ， 水利工程（专业学位）， 2021， 硕士

【摘要】 沙湾电站自2010年正式发电以来,年均发电量约20亿度,对沙湾区经济发展具有重要意义。电站运行到现在,河道边界条件、水流流态等发生了较大变化:下游河床高程总体下降,左岸泄洪闸后防冲槽发生沉降,海漫基础暴露、末端形成跌水,下游河道形成冲坑。若不进行除险加固,会逐步加剧下游河床的淘刷,继而危及海漫、消力池、甚至大坝的安全。2020年4月,电站采取临时应急防护措施,在河道下游修筑二道堰,汛后发现临时堰体在右端(临近尾水渠左堤)约有60m被冲毁。为减轻电站下游河道冲刷以保护建筑物的安全,经分析提出在下游修建钢筋混凝土的防冲尾坎优化方案。本文以沙湾电站泄洪渠首为研究对象,对原泄洪渠首、临时方案和防冲尾坎方案分别开展数值模拟计算,对比典型剖面上水面线、流场、流速的计算结果,从水力学角度分析原泄洪渠首和临时方案出现河道冲刷、二道堰冲毁的原因,探究防冲尾坎方案的可行性。主要研究成果如下(以Q=5000m~3/s的计算结果为例):(1)原泄洪渠首:水流出海漫流速高达9.89m/s,下游河道的主流靠近右岸(尾水渠左堤),对海漫末端及下游河道产生严重的冲刷,威胁尾水渠左堤的安全。(2)临时方案:海漫内水流最大流速为9.22 m/s,进入下游河道后流速有所增加,在距海漫末端40m河道的流速高达10.54m/s;二道堰后有明显急流跌水,流速增大,最大为11.86 m/s,且主流靠近右岸,严重威胁尾水渠左堤的安全。(3)防冲尾坎方案:水流出海漫流速降低为5.23 m/s,流场均匀,主流调整到河道中部,此方案能够有效减轻对下游河床的冲刷,保护海漫及尾水渠左堤。本文建立的三维模型范围不仅包括10孔泄洪冲砂闸、消力池等消能建筑物,还包括下游1120m河道及采取的工程防护措施,以保证下游河道出口断面处水流得到充分发展,提高计算的准确性。计算结果可以为沙湾电站泄洪渠首的防冲尾坎方案提供理论计算数据,对该方案的实施有一定的参考价值。更多还原

【Abstract】 The average annual output of Shawan Hydropower Station is about 2 billion kilowatt hours since operation in 2010.It is of important significance to the economic development of Shawan area.Till now,the river conditions have changed greatly,such as boundary,flow patterns and so on.The river bed elevation is generally lowered.The anti-scour trench behind the spillway sluice on the left bank settled.The foundation of the apron is exposed.There is a flow drop at the end of the apron and a hole scoured in downstream riverbed.The scouring of the downstream riverbed should be gradually aggravated without any measures.Then the safe of the apron,stilling basin,even the dam should be endangered.A temporary emergency protection project was adopted in April 2020.A temporary weir was built in the downstream river.After the flood season,right of the temporary weir,near the left dike of tailrace,was destroyed about 60 meters by rush of waters.In order to reduce the scour of the downstream channel of the power station to protect the structures,an optimization scheme is proposed,which is to build a reinforced concrete anti-scour dam in the downstream river.The research object of this paper is the head of the spillway of Shawan Hydropower Station.Numerical simulations are carried out respectively to the head of the original spillway,the temporary emergency protection project and the optimization scheme of the anti-scour dam.By comparing the calculation results of waterline,flow field and velocity on typical sections,the reasons of riverbed scoured in the original spillway and the temporary weir destroyed in the temporary emergency protection project are analyzed from view of hydraulic point.The feasibility of the optimization scheme of the anti-scour tail dam is also researched.The main research results are(the condition is Q=5000m3/s):(1)In the head of the original spillway,the maximum velocity out of the apron is 9.89m/s.The main flow in the downstream river is close to the right bank(left dike of tailrace),which causes serious scour to the end of the apron and to the downstream riverbed,and threatens the safety of the left dike of tailrace.(2)In the temporary emergency protection project,the velocity in the apron is up to 9.22m/s.The velocity increased after entering the downstream river,which is as high as 10.54m/s at 40 m from the end of the apron.There is an obvious drop behind the temporary weir.The maximum velocity increases to 11.86m/s.The main flow is also close to the right bank,which seriously threatens the safety to the left dike of tailrace.(3)In the optimization scheme of the anti-scour dam,the velocity out of the apron reduces to 5.23m/s.The flow field is uniform and the main flow is adjusted to the middle of the river.This scheme can effectively improve condition of downstream riverbed scoured,and protect the apron and the left dike of tailrace.In this paper,not only 10-hole flood sluices and energy dissipation structures are simulated,but downstream river about 1120 m and the protection measures are also included in the model.The simulation of downstream river ensures fully flow development at the outlet in the downstream river and improves the accuracy of calculation.The research provides theoretical data for the anti-scour dam scheme of Shawan Hydropower Station,and helps to the implementation of the scheme.更多还原