The objective of the study outlined in this dissertation is to investigate and develop analytical methods that can be used for displacement-based analysis and design of unreinforced and reinforced earth structures. Earthquake-triggered slope failures can pose a significant threat to both the population and a wide range of natural and man-made earth structures in earthquake-prone areas. Within the past decade, performance-based seismic design methods that calculate earthquake-induced displacement have seen increased utilization. As a compromise between simple pseudostatic analysis tools and complex numerical methods, analytical displacement-based methods can provide a reliable index of slope performance under seismic loading through their predictive calculation of permanent earthquake-induced displacements.

The first goal of this research is to provide a better understanding and insight into the performance of analytical sliding block models that are currently used in the analysis of unreinforced earth structures. For this purpose, using a well-established case history database, the predictive capability of several simplified sliding block models will be assessed for predicting earthquake-induced displacements in simple slopes and embankment dams. In an attempt to improve upon model predictions, a multi-parameter empirical correlation is also proposed for estimating earthquake-induced displacements in earth dams and embankments.

The second goal of this research will be to enhance the state of the art of displacement-based methods for the seismic design of geosynthetic-reinforced earth structures (GRES). Geosynthetic reinforcement has been increasingly utilized for stabilizing steep slopes and walls within the last few decades. Several field observations of GRES performance after major earthquakes have indicated that the current seismic design methods for these structures may be significantly overconservative. To overcome this design shortcoming, the current research presents an integrated analytical method for calculating the resultant unfactored geosynthetic force in reinforced earth structures under seismic loading conditions. The method utilizes a pseudostatic limit equilibrium approach for assessing the internal stability of a reinforced earth structure, assuming a potential rotational failure along a log spiral trace. The method can be used to determine the required tensile strength of the reinforcement for a given seismic coefficient. Alternatively, for a given reinforcement strength, the formulation can also be used to determine the yield acceleration which is required for calculating seismic displacements. For GRES design purposes, it is also desirable to have a displacement-based method that can be used to assess the required reinforcement strength under seismic conditions. To address this need, a new analytical-numerical framework is proposed for the displacement-based internal design of GRES. While a majority of the existing analytical approaches for displacement-based seismic design of GRES are developed by considering only a translational mode of failure (i.e., external sliding stability), the proposed design approach provides a rational framework for assessing the seismic displacement of GRES due to internal stability (rotational movement). This failure mechanism is more generic mechanism than the translational mechanism and also may control the required tensile strength of the reinforcement for GRES.