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

This paper presents a case study on the application of the vacuum preloadin g method for a soil improvement project in Tianjin, China. The site area wa s 50 000 m(2), 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 wat er 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 one, and the average degree of consolidation was greater than 80%, The und rained shear strength of the soil increased two- to three-fold after treatm ent. The procedures used for soil improvement, the field instrumentation pr ogramme, and the field monitoring data are described and discussed.