Abstract: To address the slope instability and foundation deformation caused by expansive soil in mining engineering,a
synergistic stabilization technique using superfine high-strength fly ash and calcium carbide slag was employed to treat expansive
soil. The effects of different mix ratios and dosages on the stabilized soil properties were investigated through compaction
tests,free swelling ratio tests,unconfined compressive strength tests at different curing ages,and scanning electron microscopy
analysis. The experimental results indicate that the optimal mass ratio of superfine high-strength fly ash to calcium carbide slag
is 7∶3,with an optimal total dosage of 15%-20%. Under these conditions,the free swelling ratio of the stabilized soil decreases to
27. 4% at 28 days age,reaching the non-expansive soil range;the unconfined compressive strength at 28 days age reaches 378. 1
kPa,which is 3. 5 times higher than that of untreated soil. Microstructural analysis reveals that the alkaline environment provided
by calcium carbide slag activates the pozzolanic activity of fly ash,generating calcium silicate hydrate and calcium aluminate
hydrate gels that fill pores and cement soil particles,forming a dense skeletal structure;calcium ions weaken the soil's swelling
potential through ion exchange. This technique effectively improves the engineering properties of expansive soil,providing an economically feasible foundation treatment solution for mining dump sites,tailings dams,and other engineering applications.