Experimental study on electro-osmosis and enzyme-promoted carbonate co-solidification of sulfate saline soil

To address engineering issues caused by salt expansion damage and insufficient structural strength in sulfate saline soils, a method combining electroosmosis with enzyme-induced carbonate precipitation (EICP) was employed to comprehensively improve the engineering properties of sulfate saline soils. Comparative experiments were designed with three grouting methods: electrode-switching grouting (EU), non-electrode-switching grouting (EM), and direct grouting (EN), systematically exploring the synergistic mechanisms of grout migration, salt removal, and strength formation under electric field effects. The experiments utilized a potential difference to drive salt ions out of the soil with electroosmotic flow, while Ca²⁺ generated from EICP hydrolysis combined with CO₃²⁻ at the cathode to form calcium carbonate cement, thereby improving the soil. The results showed that: (1) Grout injection increased the current by 32.4% to 104.8%, significantly enhancing electroosmotic drainage (up to 118%) and salt removal efficiency (up to 58.3%). The EU group, with its bidirectional ion channels formed by electrode polarity switching, achieved the highest salt removal efficiency. (2) The unconfined compressive strength of soil treated with electrode-switching grouting (EU) increased by 95.7% compared to conventional electroosmosis, with horizontal strength variability stabilized between 9.7% and 11.1%. This confirms that electrode-switching strategies can overcome the spatial heterogeneity limitations of traditional electroosmotic reinforcement. The study marks the first successful integration of EICP with dynamic electrode regulation, offering an innovative technical approach for saline soil engineering that combines efficient salt removal with uniform reinforcement.