Soil Consolidation and Vacuum Pressure Distribution Under Prefabricated Vertical Drains
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Vacuum preloading is an effective ground improvement technique for treating soft soils. Most previous research focused on the soil’s consolidation within the treatment depth of the prefabricated vertical drains (PVDs). Researches on the soil consolidation and the vacuum pressure distribution below the PVDs are very limited. Another debatable issue is the distribution of vacuum pressure within the treatment depth. Some researchers suggested that vacuum pressure decreases rapidly with depth, so there exists an effective treatment depth. Other researchers suggested that vacuum pressure does not change significantly with depth. Based on the massive monitoring data from the Shanghai Theme Park ground improvement project, it was found that all of the final surface settlements were greater than the target settlements with an average increase of 13%, and the settlement under PVDs contributed 8–18% to the final settlement. Therefore, for a project with thick soft soils under PVDs, the substratum settlement cannot be ignored. Meanwhile, the vacuum pressure below the PVDs was significant to an influence depth of up to 10 m, and the back-calculated coefficient of consolidation was 4 times higher than that determined from laboratory tests. In addition, the measured vacuum pressures were almost constant along the depth up to 20.5 m. This result indicates that the decrease of vacuum pressure with depth may not be an issue if a good sealing system is used.
KeywordsVacuum preloading Vacuum pressure Coefficient of consolidation Settlement PVD
Thanks to China Southwest Geotechnical Investigation & Design Institute for the provision of the field monitoring data. Thanks for the help of Henry Zhang (Principal Geotechnical Engineer of WSP) for the improvement of this manuscript.
- Bergado DT, Chai JC, Miura N, Balasubramaniam AS (1998) PVD improvement of soft Bangkok clay with combined vacuum and reduced sand embankment preloading. J Geotech Eng 29(1):95–121Google Scholar
- Chao V (1989) Drains and vacuum preloading pilot test. In: Proceedings of the 12th international conference on soil mechanics and foundation engineering, Rio de Janeiro, Brazil, Taylor and Francis Group, London, UK, pp 1347– 1350Google Scholar
- Chen H (1987) Analysis of the mechanism of vacuum preloading method. J Soft Soil Found Tianjin. Tianjin Science and Technical Publication. (in Chinese) Google Scholar
- Dam L, Sandanbata I, Kimura M (2006) Vacuum consolidation method—worldwide practice and the latest improvement in Japan. Hazama Corporation, Japan, Technical Research ReportGoogle Scholar
- Indraratna B, Rujikiatkamjorn C (2008) Effects of partially penetrating prefabricated vertical drains and loading patterns on vacuum consolidation. In: Proceedings of ASCE geocongress: geosustainability and geohazard mitigation, New Orleans, ASCE, Reston, VA, USA, pp 596–603Google Scholar
- Kabbaj M, Oka F, Leroueil S, Tavenas F (1985) Consolidation of natural clays and laboratory testing. In: ASTM symposium on consolidation behavior of soils, fort lauderdale, ASTM Special Technical Publication vol 892, pp 378–403Google Scholar
- Lewis WA, Murray RT, Symons IF (1976) Settlement and stability of embankments constructed on soft alluvial soils. In: Proceedings—the institution of civil engineers, vol 59, pp 571–593Google Scholar
- Masse F, Spaulding CA, Wong IC, Varaksin S (2001) Vacuum consolidation: a review of 12 years of successful development. In: Brandon TL (ed) Proceedings of 2001: Aeo-Odyssey. Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA, pp 1–23Google Scholar
- Saye SR (2002) Assessment of soil disturbance by the installation of displacement sand drains and prefabricated vertical drains. In: Symposium on Soil Behavior and Soft Ground Construction Honoring Charles C. “Chuck” Ladd, October 5–6, 2001, Cambridge, Massachusetts, United States, pp 325–362Google Scholar
- Terzaghi K (1925) Erdbaumechanik auf bodenphysikalischer grundlage. Franz Deuticke, Liepzig-ViennaGoogle Scholar