Dynamic Response Of Tubular Piles In Sand Under Horizontal Cyclic Loading

The single-pile foundation of offshore wind power is mainly composed of open-ended pipe piles,which bear very complex loads,including wave,wind and current dynamic loads.In this paper,the dynamic characteristics of open and closed tubular piles under different loading modes are studied by large-scale indoor model tests.The influences of pile diameter,load amplitude,loading path and pile tip form on the characteristics of pipe pile under dynamic load are studied by numerical simulation of pile sinking process and horizontal cyclic loading model test with particle flow PFC software.The main conclusions of this paper are as follows:(1)The indoor pile test results show that the sinking pile resistance,the lateral frictional resistance and the influence range of the closed pipe pile are larger than that of the open pipe pile,and the resistance of the open and closed pipe piles increases with the depth of the pile,and the proportion of the pile end resistance is the largest;the formation speed of the soil plug decreases with the increase of depth Tusse final height about 72% of the depth of the sinking pile,the lateral friction resistance of the pile body increases with the increase of the depth,the lateral resistance of the side friction will degenerate;the influence of open and closed pipe piles on the extrusion of piles is about 5~6 times of pile diameter.(2)Experimental study on horizontal cyclic loading of single pile in indoor has found that the cumulative displacement of pile top increases with the increase of the period,and mainly occurs in the first 100 cycles about 67% of the total;the serious disturbance of pile extrusion is three to three times the diameter of the pile,The center position of the pile is about 0.83 times times the depth of the pile,and the horizontal secant stiffness and the horizontal ultimate bearing capacity decrease with the increase of the period,and the decrease amplitude varies greatly with the loading mode,and the variation of the friction force and lateral pressure along the depth of the pile body is roughly the same,and increases gradually with the increase of depth.(3)The numerical simulation of particle flow shows that the pile resistance and lateral frictional resistance of closed pipe piles are significantly larger than that of the open pipe piles,and the resistance of the piles is linearly increased with the depth,and the lateral resistance of the pile side is degenerate.The area of severe disturbance of open and closed pipe piles is 1 time times the diameter of the pile and 1.5 times times The squeezing effect of closed pipe piles is different,the soil plug stratification is consistent with the undisturbed soil,and the final height of the soil stopper is about the double-width pile diameter.(4)The numerical simulation of particle flow shows that the cumulative displacement of pile top,the influence range of pile-soil and the decreasing amplitude of Taibiduan resistance decrease with the increase of pile diameter in the process of horizontal cyclic loading;the cumulative displacement of pile tip increases with the period,and the horizontal secant stiffness and ultimate bearing capacity of piles decrease with the increase of the period,and all occur in the first The center position of the pile is about 0.82 times times the depth of the pile body,while the lateral frictional resistance and lateral pressure of the pile body have a certain fluctuation but the overall trend is increasing,the total lateral and lateral frictional resistance decreases and the lateral pressure decreases more than the lateral friction resistance.