Internal stability analyses of geosynthetic reinforced retaining walls

Present internal stability analyses of geosynthetic reinforced soil (GRS) retaining structures are based on the limit state approach. Design methods based on this approach, such as tie-back wedge method, do not provide performance information of GRS walls and also have been found to over-predict the stress levels inside the GRS retaining structures. Working stress analyses of GRS walls are needed to improve the internal stability design as well as the performance prediction of the GRS walls.; In this research, material properties such as plane strain soil properties, low confining pressure soil dilation angle, and in-soil and low strain rate geosynthetic reinforcement properties were carefully investigated. Modeling techniques that are able to predict both internal and external performance of GRS walls at the same time were also developed. Instrumentation measurements such as wall deflection and reinforcement strain distributions of the selected case histories were successfully reproduced by numerical models developed using these modeling techniques. Moreover, the developed modeling techniques were further verified by performing Class A predictions of three laboratory test walls. Results of the Class A predictions appear to be successful as well.; An extensive parametric study that included more than 250 numerical models was then performed in this research. Influences of design factors of GRS walls such as soil properties, reinforcement stiffness, and reinforcement spacing on the performance were carefully investigated. Moreover, effects of design options such as toe restraint and structural facing systems on the performance of the GRS walls were also examined in this parametric study. In addition, analytical models of the composite GRS modulus and lateral reinforced earth pressure distribution that analyze the behavior of the geosynthetic reinforced soil were also developed in order to analyze the results of the parametric study.; In this research, effort was also made to develop the analytical model for the stress-strain relationship of a GRS composite element. The developed analytical model was used to examine the reinforcing effects of the geosynthetic reinforcement to the soil, as well as to develop composite numerical models for analyzing performance of GRS retaining structures.; Finally new performance prediction methods based on the result of the parametric study and design recommendations for the internal stability design of GRS walls were obtained.