Radial filtration model for prefabricated vertical drain treatment of slurry considering Poisson’s effect

During the vacuum preloading treatment of slurry ground, significant improvement is only observed in the soil adjacent to the prefabricated vertical drain (PVD), resulting in the formation of a protruding "soil column" with the PVD as its axis. The presence of soil column, as a unique phenomenon of slurry ground pre-treatment, leads to severe clogging and ineffective treatment results. An axisymmetric vacuum filtration model was established in the coordinate system using continuity, kinematic and equilibrium equations for both liquid and solid phases of slurry. The moving boundary condition and Poisson effect associated with soil column are also incorporated. The growth pattern and clogging behavior of soil columns were investigated through the model and verified by comparing the predicted results with particle image velocity (PIV) results. The results show that reduction of permeability coefficient within the soil column was up to 97%, indicating that the dense soil column is the essence of clogging. Furthermore, notable influence of Poisson effect and negative pressure on growth and compression behavior of soil column was observed. Low amplitude negative pressure promotes formation of relatively small loose soil columns; thereby mitigating clogging behavior.