Shake-Table Testing and FLAC Modeling of Liquefaction-Induced Slope Failure and Damage to Buried Pipelines

This paper presents Shake-Table testing and FLAC numerical modeling of liquefaction-induced large ground lateral movement and settlement, and pipeline behavior induced by soil movement. A series of laboratory Shake-Table experiments were performed using a model slope ground and model pipe buried under the crest of the slope in a box 1,800 mm long by 600 mm wide by 800 mm high. A typical 2H:1V slope was prepared with its crest at the center of the box. The model pipe had an outside diameter of 25 mm and was buried crossing the full box width and 100 mm below the crest. The above model ground was repeated for different amplitudes of input sine waves varying from O.1g to 0.25g. Observed and recorded ground failures included lateral spreading and settlement, sand boiling, time histories of excess pore water pressure buildup, input acceleration and model pipe responded acceleration. The above experimental cases were modeled using a nonlinear effective-stress modeling approach with computer code FLAC coupled with a practical-oriented pore pressure model based on cyclic stress method by Seed and co-workers (Seed, 1979). Pore water pressure buildup and dissipation were modeled using alternative stepping of fluid flow-mechanical interaction. The computed ground failures reasonably agree with the observations in the Shake-Table test. The FLAC modeling further revealed the soil liquefaction mechanism and induced ground deformation and pipe deflection.