This thesis provides a detailed study of slope reinforcement in soil slopes using soil nails, anchors and other mechanical stabilization methods. The major emphasis is on the use of soil nails in slopes formed with mostly residual soils. A comparative study has been performed reviewing the different methods of slope stability analysis, and the shear strength parameters used in stability analyses, the soil models used in numerical analyses, residual soil profiles and their detailed engineering properties used in previous studies and various computer software which are currently in use. An important conclusion concerning previous studies on slope stabilisation is that although some of them have focused on residual soils and specifically on soil nailed walls based in residual soil, there is not enough evidence available to show the effect of different parameters including soil strength, soil stiffness and also modelling assumptions on the result of stability analysis. Therefore, following a detailed discussion of the employed procedure for selection of geotechnical properties of residual soil, selection of modelling parameters for nailed wall, soil model and geotechnical software that were used, numerical models were built to perform a parametric study for stability assessment of nailed walls in residual soils.