Centrifuge modeling on seismic response of mono-pile foundation in liquefiable sand

Taiwan is located in the seismic zone and the sea bed in the western coastline of Taiwan is deposited with very loose sandy soil and may become liquefying during earthquakes. The current design code of wind turbine foundation does not give the detailed requirements of earthquake resistant design. A series of centrifuge shaking table tests of mono-pile foundations in liquefiable sandy soil was conducted at an acceleration of 80g. According to the test results the following findings were obtained. The maximum bending moment of pile in dry sand occurred at the depth of 4 m (z/L=0.21) and the maximum bending moment of pile in saturated liquefiable sand occurred at the depth of 6.4m (z/L=0.33). The induced bending moment and the pile displacement were higher if the attached mass was fixed at the higher elevation on the mono-pile foundations. The coefficient of horizontal subgrade reaction can be calculated by a p-y curve method. The values of the coefficient of horizontal subgrade reaction in shallow depths decrease while the excess pore water pressures increase during shaking. In the case of non-liquefiable soil, the values of coefficient of horizontal subgrade reaction increase with the increasing number of cycles of shaking.