Ultra-soft Ground Improvement Using Air-Booster Vacuum Preloading Method: Laboratory Model Test Study

The air-booster vacuum preloading (AVP) method has been adopted for the treatment of ultra-soft soil foundations, especially in land reclamation projects, but the air injection mode has not yet been studied. In this paper, the authors investigated the difference in improvement effect in laboratory tests of two different air injection modes, including variable pressure and constant pressure. The results show that compared with the constant pressure AVP (CAVP) method with constant air injection pressure of 75 kPa, the variable pressure AVP (VAVP) method with variable air injection pressure from 25 to 150 kPa has a better effect on ultra-soft soil improvement. Besides, if the final air injection pressure increases properly, and the air injection pressure increases with the times of air injections slowly, the soil improvement effect is significantly improved. Compared to CAVP method, VAVP method can fully utilize the air injection effect of pressurization by forming closed spaces and enhancing permeability by crack growth.