Abstract: This paper presents a case history of using vacuum preloading method improving load narrow access roads for a residential project in Bangkok, Thailand. The principals, construction technique, construction monitoring, and soil improvements aspects of the vacuum preloading method are reviewed and summarized in the paper. Conventionally, the area to be improved by this method is between 20,000 and 40,000 square meters with the length to width ratio not greater than 10. In this project, the improvement area was only 3,637 square meters with a length to width ratio of 11.22, which was much lower than the ideal area of applying vacuum preloading method. From the improvement indices such as moisture content and shear strength, these parameters show some improvement but, comparing with the conventional area and ratio of length to width, the improvement results reduced, to some extent.

Key words: vacuum preloading method, soft ground, narrow road, settlement, undrained shear strength