Performance of cut-off walls under long-term vacuum suction: A case study

Abstract

This study assesses the performance of cut-off walls in a vacuum preloading project at Lianyungang Port, China, to tackle challenges posed by ultra-soft reclaimed land. It investigates the walls’ impermeability and structural integrity by analyzing changes in hydraulic conductivity, in-situ lateral displacement, particle size distribution, and dry density both before and after vacuum suction. The introduction of a hydroxypropyl starch-based coupling agent (CA) in slurry reduces the hydraulic conductivity in the sandy matrix. Significant lateral displacement near the surface amplifies the likelihood of cracks, which lead to increased hydraulic conductivity. The cut-off wall is characterized by three zones: an erosion zone with large amount of fine particle mobility, a central effective zone with minimal deformation, and an outer tensile zone whose soil loosening leads to impermeability reduction. These findings provide valuable insights into the design and construction of cut-off walls for similar geotechnical applications and aid in forecasting the performance and lifespan of the cut-off wall.