Use of reinforced soil foundation (RSF) to support shallow foundation.

This research study aims at investigating the potential benefits of using reinforced soil foundations to improve the bearing capacity and reduce the settlement of shallow foundations on soils. To implement this objective, a total of 117 tests, including 38 laboratory model tests on silty clay embankment soil, 51 laboratory model tests on sand, 22 laboratory model tests on Kentucky crushed limestone, and 6 large scale field tests on silty clay embankment soil, were performed at the Louisiana Transportation Research Center to study the behavior of reinforced soil foundations. The influences of different variables and parameters contributing to the improved performance of reinforced soil foundation were examined in these tests. In addition, an instrumentation program with pressure cells and strain gauges was designed to investigate the stress distribution in soil mass with and without reinforcement and the strain distribution along the reinforcement. 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, and therefore higher tension would be developed for geogrid with higher modulus under the same footing settlement. The test results also showed that the inclusion of reinforcement will 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 will result in reducing the consolidation settlement of the underlying weak clayey soil, which is directly related to the induced stress. Insignificant strain measured in the geogrid beyond its effective length of 4.0~6.0B indicated that the geogrid beyond this length provides a negligible extra reinforcement effect. Additionally, finite element analyses were conducted to assess the benefits of reinforcing embankment soil of low to medium plasticity and crushed limestone with geogrids beneath a strip footing from the perspective of the ultimate bearing capacity and footing settlement. Based on the numerical study, several geogrid-reinforcement design parameters were investigated.

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