Hydro-Mechanical Characterization of AASHTO-57 and Newjersey GSB Layers under Rainfall-Induced Infiltration

Abstract

Adequate drainage is essential for the long-term performance of flexible pavements, as water infiltration from the surface, sub-surface, and sides can lead to excess pore water pressure and structural failures. The Granular Sub-base (GSB) layer plays a crucial role in facilitating drainage and providing load distribution. This study investigates the permeability characteristics of non-plastic GSB mixes prepared as per two different specifications—AASHTO-57 (open graded) and New Jersey (dense graded). A model pavement of 1.5 m × 1.5 m was constructed to replicate field conditions, and the permeability of the GSB layers was evaluated under varying rainfall intensities for 15cm thickness of GSB. The strength properties were further evaluated through the CBR test. The results indicate that the open-graded AASHTO-57 mix exhibited significantly higher permeability compared to the dense-graded New Jersey mix, making it more effective in draining infiltrated water and preventing sub-grade saturation. The findings highlight the importance of selecting appropriate GSB gradation based on local climatic and loading conditions to enhance pavement durability and reduce maintenance costs.