Assessing the Influence of Combined Stabilization on Geotechnical Properties of Subgrade Soil

Stabilization of problematic subgrade soil is considered as a sustainable solution for roadway construction. However, it is related to the strength property that is required to be reserved. Combined stabilization is implemented in the present investigation to enhance the strength and waterproofing properties of gypseous soil. Hydrated lime and cutback asphalt have been implemented in the preparation of stabilized soil. Specimens were prepared using a combination of lime and cutback and tested for unconfined compressive strength, direct shear test, and consolidation test. Specimens were tested under soaked conditions. It was observed that implementation of 7 % lime in addition to 5 % cutback can enhance the shear and compressive strength requirements of subgrade soil and control the deformation under cyclic loading. It was concluded that the compressive strength increases by (12.7, 171, and 226) % after combined stabilization when (3, 5, and 7) % of lime was implemented into the mixture while the shear strength at failure increases by (129, 56, and 28.5) % under normal loads of (27, 55, and 83) kPa respectively as compared with asphalt stabilization. The cohesion increased by 100 % after combined stabilization as compared to asphalt stabilization. However, the angle of internal friction increased by 10.5 % after combined stabilization. The deformation decreases by (15.3, and 35) % at (400 and 200) kPa effective stress respectively while the strain decreases after combined stabilization by 11.7 % at 400 kPa stress level. It was recommended that combined stabilization can enhance the geotechnical properties of subgrade soil