Abstract: Two sections of typical geotechnical instrumentation monitoring results for vacuum preloading improvements of thick soft soils at an expressway construction site in Guangdong are presented in this paper. The monitoring data indicate that the patterns of the drainage path have a large effect on the improvement results of soft soils at deep depths. Further studies demonstrate that the degree of vacuum has a different transfer pattern in various vertical prefabricated drains. A new vertical drain pattern that can effectively reduce the vacuum loss is proposed. Better soil improvement results for soft soils at greater depths can therefore be achieved.

Key words: Drainage Pattern, Soil Improvement Results, Degree of Vacuum, Soft Soil