APPLICATION OF THE EEMD METHOD TO INVESTIGATE POREPRESSURE BUILD-UPS IN AWAVE-FLUIDIZED SANDBED

摘要

The Ensemble Empirical Mode Decomposition (EEMD) method is applied to analyze wave-induced nonlinear and nonstationary pore pressure data in a resonantly fluidized response. The measured pore pressure data were first decomposed into a finite number of intrinsic mode functions (IMFs). Then, the IMFs are reconstructed to derive the excess component from the IMFs with lower frequencies and the residue. The excess pore pressures are further compared with two available methods, the linear moving average and the FFT & IFFT, to evaluate their applicability. In the end, the reconstructed excess pore pressures are analyzed to study the build-up characteristics under three different types of wave loadings. The results display that the stepped pore pressure build-ups are more likely to happen under regular wave groups and irregular waves than under monochromatic waves. It is owing to non-uniform wave loadings, under which the pore pressures can not continuously and rapidly accumulate. It is also found that the fluctuations in the excess pore pressure have close relationship with wave groupiness.