Geotechnical Considerations in Roadway Failures: Engineering Strategies for Subgrade Stabilization in Expansive Soils

Abstract

Expansive soils present a persistent challenge to roadway infrastructure due to their significant volume changes with moisture fluctuations, which often lead to pavement cracking, differential settlement, and premature failure. This paper investigates geotechnical strategies for stabilizing expansive clay subgrades to enhance the performance and longevity of roadways. A case study was conducted on a section of roadway in Dallas–Fort Worth, Texas, where three stabilization techniques including lime, lime-fly ash, and geopolymer were evaluated through laboratory testing and field instrumentation. Parameters such as unconfined compressive strength (UCS), soaked California Bearing Ratio (CBR), swell potential, and rutting were used to compare the effectiveness of each method. Results indicated that lime stabilization yielded the highest strength and swell reduction, while lime-fly ash provided comparable performance with improved environmental sustainability. Geopolymer treatment, though less effective in the short term, showed promise for long-term stabilization under optimized conditions. The study highlights that effective subgrade stabilization depends not only on strength gains but also on compatibility with site conditions, environmental concerns, and long-term performance metrics. The findings contribute practical insights for engineers and policymakers seeking resilient and sustainable roadway design in regions affected by expansive soils.