Abstract:

To address the engineering challenges posed by gully-phase soft soil subgrades in the Sichuan Basin， this study developed a composite stabilizer using ordinary Portland cement， fly ash， basalt fiber， and polyvinyl alcohol resin.The unconfined compressive strength was used as the evaluation index to optimize the mix proportion of the stabilizer to enhance its solidification effect on soft soil. Based on the reasonable dosage ranges of each material determined by single-factor experiments， a four-factor， five-level experimental scheme was designed using the central composite design response surface methodology. Quadratic regression models were established between the unconfined compressive strength of the stabilized soil at different curing ages （7， 28， 60 d） and the influencing factors， and the influence laws of individual factors and their interactions on the strength were analyzed. The results show that the established models have good fit （R2>0.952 4）. The optimal mix proportion of the composite stabilizer obtained through model optimization is m（cement）∶m（fly ash）∶m（basalt fiber）∶m（polyvinyl alcohol resin）=8.00∶4.91∶0.34∶0.46. The relative errors between the predicted and experimental strength values at various ages under this proportion are all less than 10%， verifying the model’s reliability. Mechanistic analysis indicates that the cementation from cement hydration products， the micro-aggregate filling effect of fly ash， the reinforcement by basalt fibers， and the network structure formed by polyvinyl alcohol resin collectively enhance the soil’s strength and stability. The study provides a reliable material mix proportion scheme and theoretical basis for the solidification of gully-phase soft soil in the Sichuan basin.

Key words: gully-phase soft soil, response surface methodology, stabilization mix proportion, unconfined compressive strength, stabilization mechanism