Soil improvement by the vacuum preloading method for an oil storage station

This paper presents a case study on the application of the vacuum preloading method for a soil improvement project in Tianjin, China. The site area was 50 000 m², and the soft clay treated was about 20 m thick, including a very soft muddy clay layer 4–5 m thick, formed from dredged slurry. The water contents of the clays were higher than or as high as the liquid limits. A vacuum load of 80 kPa was applied for 4 months. The ground settled nearly 1 m, and the average degree of consolidation was greater than 80%. The undrained shear strength of the soil increased two- to threefold after treatment. The procedures used for soil improvement, the field instrumentation programme, and the field monitoring data are described and discussed.