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http://dx.doi.org/10.7843/kgs.2017.33.11.73

Numerical Investigation on Seepage Stability in Offshore Bucket Cut-off Walls  

Ssenyondo, Vicent (Dept. of Civil Eng., Dong-A Univ.)
Tran, Van An (Dept. of Civil Eng., Dong-A Univ.)
Kim, Sung-Ryul (Dept. of Civil and Environmental Eng., Seoul National Univ.)
Publication Information
Journal of the Korean Geotechnical Society / v.33, no.11, 2017 , pp. 73-82 More about this Journal
Abstract
Recently, offshore bucket cut-off walls were developed to solve several problems in conventional offshore cut-off walls. In this study, a numerical analysis was carried out to investigate the seepage stability of offshore bucket cut-off walls. The ground was assumed as uniform homogeneous sand and steady state flow conditions were applied. The flow condition was compared among 2-dimensional flow (2-D), 2-dimensional concentrated flow (2-DC), and axisymmetric flow. The analysis results showed that the seepage velocities in axisymmetric flow were about 1.5 and 2 times larger than those of 2-DC and 2-D flow conditions, respectively. Thereafter, the axisymmetric flow condition was applied because the seepage flow was concentrated toward the center of the circular-shaped wall. A parametric study was performed varying bucket radius, penetration depth, total head difference between in and outside of the wall. The exit gradient, which used for the calculation of piping stability, decreased with increase of the penetration depth and bucket radius. Design charts were proposed to estimate the factor of safety and the exit gradient at various analysis conditions. Finally, the design equation was proposed to calculate the exit gradient for the preliminary design of the bucket cut-off wall.
Keywords
Numerical analysis; Seepage; Flow net; Cut-off wall; Piping;
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