Crack development in dredged sediment due to the deformation of vertical drains under intermittent vacuum preloading

Abstract

The intermittent vacuum preloading in combination with the deformable drainage system method exhibited excellent performance in treating dredged sediment. The contraction and expansion of vertical drainage system caused the formation of cracks on the surface soil. To reveal the mechanisms of crack development, laboratory model box tests were conducted on dredged sediment with different initial water contents (w₀) under various expansion strains of vertical drainage system (ε). The study investigated the crack development patterns (e.g., crack number, crack length, maximum crack width, and crack area) on surface soil near the drainage system. The results indicated that the expansion of drainage systems gradually resulted in a radial distribution of soil cracks. The threshold strain values of vertical drainage systems corresponding to the initiation of soil cracks gradually increased, with the increase of w₀. The total crack length, total crack area and maximum crack width exhibited a decreasing trend as the w₀ increased. This study also identified a critical w₀ (w₀ < water content at liquid limit) for the formation of cracks on the surface soil. The crack development patterns on the surface soil could be divided into two stages: the slow development stage (ε ≤ 10.0%) and the rapid development stage (ε > 10.0%). The cracks could potentially increase the drainage area, which further enhanced the treatment effect of dredged sediment with high water content.