Adaptive Pavement Design for Weak Subgrade Soils: A Case Study of the Almahata Road in Sudan using AASHTO 1993 Methodology

Road infrastructure is crucial to sustainable development, so flexible and rigid pavement design and evaluation are crucial for long-term security and reliability. This study examines the Almahata road in Aljazeera State, Sudan, where weak subgrade soil causes problems. The main goal is to evaluate the road’s structural and geometric design according to AASHTO 1993 guidelines, emphasising surface drainage and material selection. Complete field investigations were conducted, collecting soil samples from four trial pits at various depths. Particle size distribution, Atterberg limits, specific gravity, compaction, California Bearing Ratio (CBR), and Resilient Modulus (MR) were tested on these samples. AASHTO and Unified Soil Classification Systems divided the soils into five groups. The recommended design CBRs is 4.0% for the subgrade, 32% for the sub-base, and 62% for the base layer. A CBR range of 4.0% to 62.0% was found. The final pavement structure had a 525 mm thickness, 75 mm Hot Mix Asphalt, 200 mm base, and 250 mm sub-base layers. Reduced asphalt thickness was offset by increased base and sub-base layers to cut costs. This study shows that adaptive design in pavement construction is cost-effective and structurally sound. Future research should examine these designs' long-term performance under increasing traffic and changing environmental conditions.