Doctor of Philosophy (PhD)


Civil and Environmental Engineering

Document Type



This research study aims at investigating the potential benefits of using the reinforcement to improve the bearing capacity and reduce the settlement of shallow foundations. To implement this objective, a total of one hundred seventeen tests were performed to study the behavior of reinforced soil foundation. The test results showed that the inclusion of reinforcement can significantly improve the soil's bearing capacity and reduce the footing settlement. The geogrids with higher tensile modulus performed better than geogrids with lower tensile modulus. The strain developed along the reinforcement is directly related to the settlement. The test results also showed that the inclusion of reinforcement can redistribute the applied load to a wider area, thus minimizing stress concentration and achieving a more uniform stress distribution. The redistribution of stresses below the reinforced zone can result in reducing the consolidation settlement of the underlying weak clayey soil. Insignificant strain measured in the geogrid beyond its effective length of 4.0~6.0B indicated that the geogrid past this length provides negligible reinforcement effect.

The scale effect on the results of model footing tests was studied using FEA program ABAQUS. Finite element analysis results indicate that the scale effect of reinforced soil foundation is mainly related to the reinforced ratio (Rr) of the reinforced zone.

The failure mechanisms of reinforced soil foundation were proposed based on the literature review and experimental test results. Stability analysis including the effect of reinforcement has been conducted based on these proposed failure mechanisms. The new bearing capacity formula with the contribution of reinforcements to an increase in bearing capacity was then developed for reinforced soil foundation. A reasonable estimation on the tensile force along the reinforcement was proposed. The predicted bearing capacities of reinforced soil foundation by using the methods of this study are generally in good agreement with the field test results of previous research for reinforced sand and this study for reinforced silty clay. The proposed methods also provide a good prediction of laboratory model test results of this study.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Murad Y. Abu-Farsakh