The book concerns influence of unsaturated soils of earth dams. The effective stress variable has been used in the Mohr-Coulomb theory for predicting the shear strength of saturated soils. In this book is considered a clay core of earth dam that water level is supposed. Tree types of soil are chosen for calculation of unsaturated cohesion with two mentioned methods, Eq. Matsushi and Matsukura and Eq. Lee et al.This book shows the influence of the water level on the cohesion profile in the dam. Also, the book concerns the seismic induced response of earth dams. Analysis is conducted by a non linear finite difference modeling of the earth dam using the software FLAC3D. The behaviour of the Shell and core of the dam is described by a Mohr coulomb criterion. The material properties have been chosen more close to reality. For this book, the dynamic input be applied in terms of velocity for both sinusoidal and earthquake velocity waves at the foundation base of the model in the horizontal direction.