Journal Published Online: 30 April 2018
Volume 47, Issue 2

Model Tests of Buoyant Force on Underground Structures

CODEN: JTEVAB

Abstract

Conventionally, buoyant foundations are designed based on Archimedes’ principle, by which the buoyant force is computed by simply measuring the weight of groundwater that is displaced. However, soil at shallow depths is generally unsaturated and should be considered as a multiphase porous medium with heterogeneous properties. The efficacy of the Archimedes’ calculation of buoyant force is questionable because recent field evidence indicates that the measured buoyant force is actually much smaller, and the foundation design is always conservative. This article presents a series of model tests on shallow foundations embedded in different surrounding types of materials, such as pure water, clay, and sand to clay-sand composites. Both the transient and sustained hydrostatic uplift forces were measured. It has been demonstrated that the measured buoyant force increased with time and was always less than the theoretical value. A reduction coefficient was consequently suggested to scale down the Archimedes’ buoyant force for use in design. For shallow foundations in clay, a value of 0.3–0.4 should be used to evaluate the transient uplift force, and a higher value of 0.7–0.8 is recommended for the estimation of the steady-state buoyant force. For sand, the reduction coefficient varies between 0.85 and 0.95 for transient and sustained uplift conditions, respectively.

Author Information

Ni, Pengpeng
School of Civil and Environmental Engineering, Nanyang Technological University, Singapore, Singapore
Kang, Xin
Department of Geotechnical Engineering, College of Civil Engineering, Hunan University, Changsha, China
Song, Linhui
School of Physical and Mathematical Sciences, Nanjing Tech University, Nanjing, China
Mei, Guoxiong
Key Laboratory of Disaster Prevention and Structural Safety of Ministry of Education, College of Civil Engineering and Architecture, Guangxi University, Nanning, China
Zhao, Yanlin
Key Laboratory of Disaster Prevention and Structural Safety of Ministry of Education, College of Civil Engineering and Architecture, Guangxi University, Nanning, China
Pages: 20
Price: $25.00
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Stock #: JTE20170017
ISSN: 0090-3973
DOI: 10.1520/JTE20170017