丰满水电站重建工程老坝拆除缺口方案研究

Study on scheme of demolishing notch on old dam for Fengman Hydropower Station Reconstruction Project

丰满水电站重建工程新建碾压混凝土重力坝位于老坝下游120 m处,为保证新建机组发电过流并满足大坝泄洪要求,新坝建成后,需对老坝进行局部拆除,将大部分老坝结构留在库区,从而利用前置挡墙效应分层取水,缓解夏季下泄低温水。通过水力学计算分析,方案设计考虑满足厂房坝段及溢流坝段过流条件要求,结合水工模型试验成果、坝前地形、环境保护等条件,进一步优化老坝拆除缺口的拆除高程和宽度,确定缺口拆除范围。对于老坝拆除后形成的高27.5 m的巨大缺口,其两侧侧立坝段拆除高程以上的横河向抗震安全性需要验算,采用有限元时程法对地震情况下缺口两侧挡水坝段在高程240.20 m层面的稳定和应力进行了复核。为避免水流对缺口的冲刷和冻融破坏,防止缺口处坝体混凝土老化后脱落,缺口底部和两侧现浇混凝土防护。

The new RCC gravity dam of Fengman Hydropower Station Reconstruction Project is located at 120 m of the downstream of the old dam.In order to ensure the flow-passing for the power generation of new generating unit and meet the flood discharge requirement of the dam,the old dam is necessary to be partially demolished and remain the most of the old dam structure in the reservoir area,so as to take water in layers by means of the effect of the front retaining wall for alleviating the discharge of the low-temperature water in summer.Through the relevant hydraulic analysis and calculation,the requirements for the flow-passing conditions for the powerhouse dam section and the overflow dam section are considered and satisfied in the scheme design,while the elevation and width of the demolishing notch of the old dam are further optimized and the demolishing range for the notch is determined in combination with the conditions of the result of the hydraulic model experiment,the topography in front of the dam,the environment protection,etc.For the 27.5 m-high huge notch formed after the demolition of the old dam,the checking calculations are necessary to be made for the river-crossing seismic safeties of the lateral dam sections above the demolishing elevation on both the sides of it,and then the stabilities and stresses at the level of 240.20 m of the water retaining dam sections on both the sides of the notch in the case of earthquake are checked with finite element time-history method.For avoiding the erosion and freeze-thaw damage from water flow and preventing the dam body concrete from falling off after aging at the notch,the bottom and both the sides of the notch are protected with cast-in-place concrete as well.