The subgrade supports the pavement structure and distributes traffic-induced stresses into the underlying ground. Weak, highly plastic soils may exhibit low shear strength, high compressibility, moisture sensitivity, rutting, differential settlement, and premature pavement deterioration. Mechanical stabilization improves such soils by modifying gradation and particle interaction without chemical reactions. NH-716 connects Chennai and Tirupati. Package-I extends approximately 43.95 km from Tiruvallur to the Tamil Nadu–Andhra Pradesh border and includes a four-lane access-controlled highway with paved shoulders. The investigated soil had a four-day soaked California Bearing Ratio of 1.8% and unconfined compressive strength of 75 kPa, indicating inadequate support for direct use as a pavement foundation. This study investigates a fixed 70:30 sand–gravel blend at different dosages to characterize the soil, evaluate compaction, determine unsoaked and soaked California Bearing Ratio, assess unconfined compressive strength with curing period, and identify a practical dosage for field evaluation.

Piyush Kumar Upadhyay, Dr. Sumnotam Patel,"Mechanical Stabilization of Weak Highway Subgrade Using a 70:30 Sand–Gravel Blend: A Case Study of NH-716 Package-I" International Journal of Advanced Multidisciplinary Research and Educational Development, V2(4): Page(607-610) July - August 2026. ISSN: 3107-6513. www.ijamred.com. Published by Scientific and Academic Research Publishing.