| This thesis reviews the most frequently used two-dimensional (2-D) and the few available three-dimensional (3-D) slope stability analysis methods. It is concluded that commonly adopted two-dimensional analysis can not actually represent practical three-dimensional problems and that most of the available 3-D analysis methods have too many limitations to be used for conical excavations, such as those proposed by CP&L for thermal energy storage. The main objective of this research work is to develop a 3-D model which can accurately simulate an actual 3-D conical excavation and to apply this model to analyze the stability of unreinforced and soil-nailed conical excavations. Based on the defined 3-D model, a parametric study is performed and design charts are developed that allow one to estimate the critical factor of safety before the execution of an excavation. A computer program is developed to evaluate the factor of safety for unreinforced slopes ranging from 2-D plane strain to 3-D cylindrical and conical geometries.; For soil that exhibits insufficient cohesion or does not provide the desired factor of safety, soil nailing is a potential excavation support strategy. A stability analysis method for soil-nailed excavations is presented, based on the 3-D model defined in this work. The computer program developed can also be used to automatically search for the critical failure surface and the critical factor of safety for soil-nailed excavations.; Design charts, which reflect the effect of ground water table elevation, and excavation geometry including depth of cut slope, inclination, and the toe of excavation radius, on the stability of unreinforced and soil-nailed conical excavations, are developed. For soil-nailed excavations, the effects of soil properties and soil nailing parameters, including the nail length, horizontal and vertical spacing, nail diameter and pullout resistance on the critical factor of safety are analyzed. At a desired factor of safety, the charts can be used to choose suitable installation parameters to reach an economical design. |
