Soil improvement by vacuum-surcharge preloading method in Wugang Port

This paper presents a case study on the application of the vacuum-surcharge preloading method for a soil improvement project in Wuhan, China. In order to meet the need of land use of Wuhan Petroleum and Chemical Plant, Wugang Port will be filled. Before filling, the soft ground must be improved. Because the requirements of bearing capacity and post-construction settlement are very rigorous and the allowable construction period is very short, it is difficult to make the design of ground improvement. The site area which needs to be treated is nearly 130,000 m(2) and the geological conditions are very complex. The distribution of soft clay is extremely uneven, and the thickness of soft clay ranges from 1 m to 19 m. In order to complete the construction within the expected period and lower the construction cost, the scheme of vacuum-surcharge preloading has been selected after detailed comparison of several available schemes. The treated area by vacuum-surcharge preloading is about 90,000 m(2). According to the different geological conditions, the treatment area is divided into six zones. There is four various pattern of prefabricated vertical drains layout in the six zones respectively. A vacuum load of 80 kPa was applied for 135 days. The average degree of consolidation of the soft ground was greater than 90%. The engineering practice indicates that vacuum-surcharge preloading method is appropriate in this site and the effect of treatment is excellent. The successful experience in this project is beneficial for other practical cases under similar complex geological conditions.