Reverse vacuum preloading method for overlying backfill soil of blown silt foundation

A reverse vacuum preloading method is proposed to address the problems of poor reinforcement effects of deep soil and vacuum loss when the traditional vacuum preloading is used to treat silt foundation. This method uses a reverse drainage plate to apply vacuum pressure to the deep soil directly. The influences of backfill soil thickness on the reinforcement effects of reverse vacuum preloading method are studied through the indoor model experiments. Compared with the traditional vacuum preloading, the reverse vacuum preloading method increases the drainage volume by 16.46%, increases the vane shear strength of the deep soil by 20.50%, and significantly improves the overall reinforcement effects. With the increase of the backfill soil thickness, decreasing the rate of the vane shear strength in the silt layer along the depth direction is significantly reduced, and the treatment effects are more uniform. In addition, through on-site comparison between the reverse and traditional vacuum preloading methods, it is found that the surface settlement of the soil treated by the reverse vacuum preloading method increases by 15.70%, the dissipation of pore pressure in deep soil increases by 26.20%, and the average vane shear strength increases by 21.12%. Therefore, it is concluded that the reverse vacuum preloading method is an effective foundation treatment method, especially for deep soil reinforcement.