This study develops an advanced coupled hydromechanical finite element model to better explain natural fiber-reinforced expansive soils under wetting and drying cycles, addressing soil-structure interaction due to moisture change. The model uses an innovative multiphase FEM paradigm to encompass moisture transfer processes, swelling pressures, and non-linear stress-strain behavior. Experimental verification confirms the accuracy and dependability of the model under different types of field conditions.The experimental validation gives the confidence of accuracy and reliability of the model under different field situations. The systematic study of the natural fibers shows that very satisfactory reinforcement, in the range of 0.5–2.5% fiber content can reduce swelling potential by 35–50% while increasing the shear strength up to 20–30% more than that of unreinforced soil. Parametric studies also show the effects of fiber aspect ratio, denier, spatial distribution on hydromechanical response, in particular better stress transfer and smaller differential settlement under foundations are predicted by the model. To improve the readability for users, a flow chart of the coupled model is also shown in this section. Significant trade-offs between cost, environmental impact, and performance are revealed by a comparison with conventional stabilization techniques. The findings indicate that natural fiber reinforcement offers an affordable, low-carbon substitute that complements sustainable building objectives. Beyond its technical implications, this study establishes a novel link between computational and experimental geotechnics. It supports environmentally friendly soil development techniques by providing quantifiable design standards and introducing a trustworthy, predictive modeling tool.