Doctor of Philosophy (PhD)


Civil and Environmental Engineering

Document Type



The objectives of this study are to investigate and evaluate the benefits of inclusion of geogrids in two types of geosynthetic reinforced soil/aggregate structures—e.g. reinforced soil foundations (RSF) and reinforced base aggregate in flexible pavements, thus shedding the light on the design of these reinforced structures. Two different finite element models were developed using ABAQUS software. The first model was used to investigate the bearing capacity and settlement of RSF and to perform parametric study on the effect of different design parameters on the performance of RSF. The second model was used to analyze the performance of geogrid reinforced bases in flexible pavement in terms of surface rutting, which was also used to perform parametric study on the effect of different design parameters on the performance of reinforced pavements. Based on the results of finite element analyses, multiple regression models were developed to estimate the benefit of reinforced geomaterial structures under different combination of design parameters. The results of finite element analysis on RSF showed that the inclusion of reinforcement, in general, results in increasing the bearing capacity and reducing the settlement of the reinforced soil. The benefit increases with increasing the tensile modulus and/or number of reinforcement layers. The results also showed that the effective reinforcement depth is about 1.5 times the footing width, and there exists an optimum depth of first reinforcement layer where the highest bearing capacity can be achieved. The results of finite element analysis on geogrid reinforced bases in flexible pavements showed that the use of geogrid reinforcement reduces the lateral strains within the base and subgrade layers, reduces the vertical strains on top of subgrade layer, and hence significantly reduces the surface permanent deformation (or rutting) of pavements. In terms of traffic benefit ratio (TBR), the geogrid base reinforcement helps increasing the service life of pavements, with TRB values of up to 3.4 were obtained for pavement sections over weak subgrades. The finite element analysis clearly demonstrated that the geogrid improvement increases with increasing the geogrid tensile modulus and with decreasing of both the base course layer thickness and the subgrade strength.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Abu-Farsakh, Murad Y.