This study investigated the mechanical properties of foundation soil solidified with geopolymer binder materials， replacing traditional cement in cement-soil mixing piles. The experiment used sodium silicate to activate montmorillonite， slag fly ash， and carbide slag to form a geopolymer binder for soil solidification. The unconfined compressive strength of the solidified foundation soil was tested for various proportions， along with strength variations of two groups of specimens after immersion in HCl solution （pH=5） and 5% Na?SO? solution for 7， 14 and 28 days. X-ray diffraction （XRD） and scanning electron microscope （SEM） were used for composition and microstructure analysis. The results indicated that， compared to using slag alone， the addition of a small amount of fly ash enhanced the compressive strength of geopolymer-solidified soil. Incorporating 5% montmorillonite participated in the geopolymer reaction， adsorbed moisture， and filled pores， thereby increasing the strength of the geopolymer-solidified soil. However， excessive montmorillonite content adversely affected the mixture due to its water-absorbing and expanding properties. Using a sodium silicate modulus of 0.8， with a dosage of 12%， 5% montmorillonite， and a slag-to-fly ash ratio of 9∶1， the geopolymer-solidified soil achieved a compressive strength of 3.44 MPa after 28 days of standard curing. After 28 days of immersion in HCl solution， the strength was decreased by 26.2%， and after 28 days in NA2SO4 solution， it was decreased by 17.4%. The compressive strength of the geopolymer-solidified soil was 2.73 times that of cement-solidified soil， demonstrating excellent resistance to acid and sulfate attack.