Influence of Compaction Technique on Shear Strength of Modified Subgrade Soil

Abstract

The subgrade soil is considered as the foundation for the roadway structure, it is responsible to provide the required stability for the overlaying pavement layers and to limit the deformation due to traffic load repetitions by furnishing homogeneous stress distribution. For poor soil condition, grid reinforcement or Asphalt stabilization techniques are usually implemented to control the deformation and improve shear strength of poor granular subgrade soil. In this work, the unconsolidated undrained Triaxial test was implemented for comparatively assessing the impact of asphalt stabilization or grid reinforcement on shear strength of the improved subgrade soil. Soil samples have been treated with cutback asphalt and specimens were prepared. Another type of grid reinforced soil specimens was also prepared. Cylindrical Specimens with height and diameter of (77.4 and 38) mm respectively have been prepared in the laboratory using two compaction techniques, (static and impact) compaction to achieve a target density. Specimens were tested in the Triaxial apparatus to determine its shear properties. Data have been analyzed and compared. It was concluded that the (impact compaction) exhibit significant increase in shear strength for asphalt stabilized soil and grid reinforced soil. On the other hand, the insertion of the grid reinforcement into the specimen at half of its depth exhibits the best location for providing the shear resistance.