Study On Dynamic Response Characteristics And Safety Monitoring Indexes Of Apron Slabs In Plunge Pool Of Ertan Hydropower Station

The safety of apron slabs in plunge pool of high dam is a key problem to successor failure of flood energy dissipation. In recent years, a batch of high dams is underconstruction in China. There are two sides about the research of plunge pool. One side,based on mechanics, the aim is explaining mechanism of reciprocity of high speedwater and apron slabs and finding the stability condition of apron slabs in plunge pool.It is much helpful to design the plunge pool. The other side, the aim is designingsafety monitoring system that is composed of observation system and safetymonitoring indexes. This time, we observed the flood discharge vibration of apronslabs in plunge pool. We researched safety indexes of plunge pool systemically usingsome signal processing technologies and brought forward a series of safetymonitoring indexes. The main achievements of this dissertation include as follows:(1) The random vibration of apron slabs in plunge pool is caused by fluctuatingpressure of vortex in plunge pool and impact pressure of high speed water. We had aprototype observation and analyzed the results in time-amplitude-frequency domain tofind the vibration feature. We discussed the disciplinarian of fluctuating pressure anddestroy mechanism of apron slabs. Finally, safety monitoring indexes of apron slabsin plunge pool are established.(2) The Fractal feature is confirmed by analyzing the vibration signal of apron slabs inplunge pool. Firstly, the box dimension and correlation dimension of the vibrationsignal had been calculated and connected with the dimension of the figure structuredrawn in the phase space of the dynamic system. The fractal characteristics ofvibration signal of apron slabs in plunge pool are researched, and the application ofthe method of fractal self-affine and fractal interpolation to restruct and forecast thevibration of the plunge pool is also presented.(3) Signals are decomposed in different frequency phase by wavelet analysis. Energypercent is calculated in these frequency phases. These values show the size offluctuating pressure energy in relevant frequency phase. Then, we can know theenergy distributing from ration. The vibration signal is decomposed into a number ofintrinsic mode function (IMF) components in Empirical Mode Decomposition method.We had a useful explore in vibration signal processing of apron slabs in plunge poolby using this new time-frequency method.