Centrifuge Modeling of Laterally Loaded Monopile During Different Liquefaction Phases

The monopile response to lateral load under different liquefaction phases via centrifuge modeling tests is reported in this paper. The test was performed in viscous scaling mode to match the loading time and flight speed at a centrifuge acceleration of 80 g. A mixture of methylcellulose powder in water increased the viscosity by 80 times compared with water at a concentration of 0.47%. The seismic input is applied with a frequency of 1 Hz to achieve soil liquefaction. During the test, the monopile received the lateral load. The liquefaction regime was divided into four distinct phases based on the excess pore water pressure ratio during loading: total liquefaction, two tests during the period of degradation of pore pressure when the excess pore water pressure ratio was 0.67 and 0.32, and the last test at the end of liquefaction. The results reveal that pore water pressure distribution slightly differs in the free field and surrounding pile. The shallow layer started to liquefy early in response to the ground acceleration. The entire monopile body rotated owing to 0.48 m of pile head displacement during full liquefaction when the lateral load applied reached 290 kN. During the liquefaction regime, the profile of the pile behaviors migrating from a slender pile to a rigid pile is a significant discovery in this study. A large shear force appeared one-third of the pressure to the bottom of the monopile, and the maximum bending moment location became deeper, with a value of 65% greater than at the end of liquefaction.