Effects Of Excess Pore Pressure On P-y Curves Of Pile Foundation In Silt

In recent years, offshore wind power has been developed rapidly in many countries owning rich offshore wind resources because of the advantages such as the great and stable wind speed, the low cost, the short period of constructing and the small limit on the noise. Mono-pile foundation is widely used for offshore wind turbines relying on its characteristics. Meanwhile, p-y curves play a significant role in foundation designing. Therefore, it is important to study different p-y curves to adapt the soil priority and state.The paper studies the p-y curves of silt in Yellow River Delta with the help of laboratory experiments after summarizing the results of domestic and foreign scholars. The experiments make the excess pore pressure produced depending simulative waves and beating. At the same time, lateral loads and vane shear tests are applied. Ultimately, the distribution of bending movements, lateral displacements, soil resistance and the relevant shear strength in different states of pore pressure can be obtained; p-y curves are established and computed using Lpile. The main work and conclusions can be drawn as follows:(1) After soil in position, excess pore pressure evanished in seven days rapidly and became stable after 15 days. The pore pressure ratio decreased about 0.4 in 13000s in the depth of 35cm under mud surface, the dissipation rate of which was bigger than the depth of 65cm and 75cm. Therefore, the phenomenon indicates that the shallow dissipation is faster than the deep. Also, lateral static loads to the pile hardly influence the distribution of pore pressure, which can be ignored.(2) After the lateral loading test, the peak bending movements of three experiments are all in the depth of 0.2m to 0.3m under mud surface, and the three peak bending movements 45N·m、32 N·m and 28 N·m correspond with three pore pressure ratios respectively, which indicates that bending movements decrease with the increase of pore pressure ratio on account of excess pore pressure.(3) According to the shear strength data, soil shear strength increases with the enlargement of depth. What’s more, soil shear strength decreases as the saturability increases under the same condition.(4) The relationship between soil resistance and pore pressure ratio is analyzed and the reduction coefficient is defined as C. C increases along with the enlargement of depth, but it is hardly influenced by lateral displacement. What’s more, C decreases with the increase of pore pressure ratio in the depth of 2B to 8B. After fitting, the slope of the trend, which decreases with the increase of depth, distributes in the range of -0.48 to -1.73.(5) The p-y curves obtained from the 3 experiments are computed using Lpile. The results indicate that the maximums of displacement and bending movement all increase in different degrees with the increase of pore pressure ratio. The pile becomes easier to be destroyed because of the reduction on the soil strength resulting from the appearance of excess pore pressure. Therefore, pore pressure is a key factor which should be considered seriously when designing pile foundations.