Comportement des pressions interstitielles et leur variabilité temporelle dans le noyau argileux du barrage Ain Zada (Est Algérien).

The Ain Zada dam (Eastern Algeria) is built in 1986 with rockfill and clay core. The behavior in the medium and long term of overall functioning of clay core has been evaluated by pore pressure (PI) and reservoir level (NR) using: univariate spectral analysis continues wavelets analysis, multi-resolution, fractal analysis and rescaled range analysis (R/S). Spectra PIs present high peaks for very low frequencies caused by the trends and sudden changes in their time series and NR. This signal indicates a non-stationary process. Noise analysis place PIs chronic in Brownian noise anti-correlated, random and structured types indicating an increasing variation in the past implies a decreasing variation in the future. This would be favorable for the stability of the structure and confirms the reality of seasonal periodicities and effects of swelling clays. The continuous wavelet analysis reveals the existence of non-stationary structures in the long term. In general, all cells have a homogeneous distribution of the exclusive power to large scales (annual trend). This would correspond to the dissipation at long term of PIs in the clay core. The energy distribution of PI and NR according to the scale, shows that their variance is very low in the short and medium term. The cross-level multiresolution analysis by level scale quantifies the degree of the causal relationship NR-PI according to the scale decomposition. The intercorrelation confirms their relationship over the long term. The moment distribution in logarithmic coordinates shows that it is fractal and the heterogeneity is continuous on the interval scale of 1-500 days. This multifractal character translates the variations of PIs do not respond to same mechanisms in the short, medium and long term. The clay core through PIs keeps the heterogeneity observed at retention level (NR). The system does not filter information and also keeps that observed in the rainfall distribution. The log-normal distribution of singularities of NR varies considerably depending on the scale and in a less degree of PIs which their non-stationarity follow an almost linear progression. The R/S shows that the PIs in the clay core are non-stationary and past and future values are closely related. [ABSTRACT FROM AUTHOR]