Load-Deformation Behavior of Woven Geotextile–Reinforced Slag–Subgrade Systems

Abstract This study investigates the mechanical performance of slag placed over subgrade soil, with a focus on the reinforcing role of woven geotextiles under cyclic loading. To achieve this, two complementary experimental approaches were employed: large-scale box tests simulating repeated traffic loads with a peak load of 20 kN applied over 100,000 cycles and resilient modulus ( M R ) tests conducted in accordance with AASHTO T 307. Results showed that the inclusion of a woven geotextile layer substantially enhanced both the permanent deformation and resilient behavior of the combined slag–subgrade system. In the large-scale tests, geotextile reinforcement reduced permanent deformation beneath the loading plate by 70.5%, compared to the unreinforced case. Similar improvements were observed around the loading plate, indicating enhanced lateral confinement. Stress–strain responses confirmed stabilized behavior in the reinforced sections, free from peak stress surges and instability. Furthermore, resilient modulus results demonstrated a consistent increase in M R values across all stress stages, confirming improved recoverability and stiffness under repeated loading. Overall, the combined findings reveal that the utilized geotextile reinforcement effectively suppresses plastic deformation while improving the resilient performance of granular layers, underscoring its potential as a structurally reliable solution for pavement base systems incorporating slag.