Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)

First Advisor

Ilan Juran


The considerable development of the geosynthetics and their increasing use in soil reinforcement made it necessary to develop methods of measuring the interaction properties and modeling load transfer in reinforced soil structures. The current testing procedures demonstrate significant limitations related to the testing methodology and data interpretation. In order to address these limitations, a pull-out box and direct shear box were constructed. The design of these boxes overcomes most of theses limitations and provides the capability of conducting displacement-rate controlled tests for the evaluation of short-term behavior of the soil-reinforcement system, and load-controlled tests to evaluate their time-dependent performance. The accuracy of the testing facility was evaluated through comparison of test results with those provided by the manufacturers. The reproducibility of test results were evaluated through repetitive tests performed on the geogrids under the same testing parameters. A parametric study on the geogrids under different testing conditions (i.e. pull-out displacement-rate, confining pressures, soil compaction, soil density and boundary conditions) was conducted to evaluate the equipment sensitivity to the variations in testing conditions and to provide a data base for the evaluation of the effect of these parameters on the interface properties. A data analysis procedure was established to determine the interface properties and the confined material characteristics of the geogrid reinforcement. The applicability of the load-transfer model was evaluated through comparison between the interface parameters evaluated from pull-out tests with those measured directly from the tests performed in the large direct shear box. The interface properties and confined material characteristics of the geogrid reinforcement were utilized in a design model for the stability analysis of reinforced soil structures. This model is implemented in a computer program to calculate the forces in the reinforcements and to predict the failure plane. The maximum tension force at each reinforcement level and the inclination of failure surface can be predicted for different soil and reinforcement characteristics. In order to evaluate the design assumptions considered in this model, the predicted tension forces were compared with those measured in model and full-scale model walls and embankments of different soils and reinforcements.