Abstract: To study time-dependent airtight capacity, impermeability and breadth of mixing silt wall in vacuum preloading by soil-water character, comprehensive tests were carried out. It was found that mixing silt wall treated with pile cap at the intersection of two preloading areas and 2-rows’ inequilengthy pile wall using at the periphery was feasible to solve mixing silt wall subsiding and crazing and insure the durability of airtight capacity. A case study with large-scale area of 0.84 km2 is presented involving the hydraulic fill treated with vacuum preloading in Nansha Harbor; and airtight capacity of mixing silt wall and soil improving effects were analyzed by the distributing and changing in pore-water pressure, underground water table and vacuums; and it was concluded that mixing silt wall with breadth 1m and permeability less than 10-6 cm/s met the need of the airtight capacity under vacuum of 85 kPa.

Key words: vacuum preloading, mixing slurry wall, permeability, airtight capacity, application technique