This book uses the upper bound limit analysis for determination of stability numbers for a two-layered soil slope both for an associated flow rule material and for a homogeneous slope with non-associated flow rule material. The effect of the pore water pressure and horizontal earthquake body forces was also included in the analysis. The results have been given in the form of non-dimensional stability charts, which can be used for readily obtaining either the value of the critical height or the factor of safety. An attempt has also been made in this book to study experimentally the effect of the frequency of the excitation and the addition of non-plastic fines on the liquefaction resistance of the material. Shake table studies, generating uni-axial sinusoidal horizontal vibrations, were carried out for this purpose. The peak magnitude of the pore water pressure tends to be higher for the excitation with smaller frequency especially at greater depths from the ground surface. The addition of non-plastic fines tends to increase the magnitude of the settlement as well as the increase in the pore water pressure.