Evaluation of Using Geosynthetic Material and the Process of Grouting to Improve Pavement Performance over Sand Dunes Subgrade

Transportation engineers face many problems in using sand dunes available in huge quantities through the desert areas in Iraq as construction materials for roads. This study consists of using sand dunes as local material in road construction. Two approaches are adopted to achieve this goal; the first is carrying out laboratory tests through simulation of three layers of paved road, using a steel box model where subgrade layer represented by sand dunes at relative density 55.7% (in situe value). The study oriented as well to the improvement of sand dunes through using reinforcement with two types of geosynthetic material. Two models were studied, one of which is reinforced by single layer of geotextile at subbase- subgrade interface and the other using single layer of geogrid at the same depth to improve the subgrade, grouting technique is used through the injection of the subgrade with a mixture of cement, bentonite, and water. Using of geotextile and geogrid, leads to increase the number of passes 108.53%, 78.05% respectively. The using of injection technique increase the number of passes about 18.29%. FE approach using abaqus program was applied to find out displacement distribution through build pavement structure model. The results obtained from both laboratory and finite elements are very much encouraging with using sand dune as construction materials for roads. However, using reinforcement in between subbase- subgrade interface also satisfied the minimum stability requirements for roads foundation structure with sand dunes as subgrade layer.