Effect of Clogging on Large Strain Consolidation with Prefabricated-Vertical Drains by Vacuum Pressure

Clogging will inevitably occur while using vacuum preloading method to process super-soft soils with high water content. How to quantitatively evaluate the effect of clogging on the consolidation behavior is a key issue to be solved. Based on NALSC (negative axisymmetric large-strain consolidation) model, considering the "internal clogging" and the "external clogging", a calculation method by using parameter "clogging rate" to reflect clogging problem is proposed for single-well consolidation theory. Effects of clogging rate and clogging occurred time on Us (degree of consolidation defined by strain) and Up (degree of consolidation defined by stress) are investigated. Differences of the effect of clogging on consolidation degree are determined between large-strain and small-strain consolidation theory. The results show that, the larger the clogging rate, the smaller the degree of consolidation of the soil at the same consolidation time. Effect of clogging on Up is greater than Us. The earlier the clogging occurs, the smaller the degree of consolidation at the same clogging rate. Influences on the degree of consolidation for large-strain and small-strain theory are the same. Consolidation rate of soil is determined to a certain extent by the "generalized clogging parameter mu". The "external clogging" has a greater influence on the degree of consolidation than the "internal clogging" at the same clogging rate.