Investigating combined effects of saturation–desaturation cycles and cyclic stress resistance of reinforced biopolymer-treated soil

Abstract

Throughout their service life, subgrades endure significant stress from cyclic traffic and seasonal moisture fluctuations. This study aims to evaluate the moisture variation and cyclic stress resistance of reinforced and biopolymer-treated soils, which were treated with varying percentages (0.25%, 0.5%, 0.75%, and 1.0%) of xanthan gum (XG) and sisal fiber, to determine the level of tolerance a subgrade can sustain. Wetting–drying (W-D) cycle tests, unconfined compressive strength (UCS) tests, and dynamic resilient modulus (DRM) tests were conducted to assess the resistance of the treated soils to moisture variation and cyclic stress. The findings indicate that biopolymer-treated specimens retained over 95% of their original mass after 15 cycles, whereas fiber-reinforced soil exhibited a 9.1% loss in mass. Furthermore, the DRM of the reinforced soil improved, demonstrating greater resistance to cyclic stress compared to biopolymer-treated soils. Fiber-reinforced soils exhibited strain-hardening responses at low cyclic stress levels and maintained stress tolerance even at high cyclic stress levels without signs of strain deformation. Conversely, the UCS of the biopolymer-treated soil surpassed that of the fiber-reinforced soil due to the brittleness of the specimens.