Shaking Table Test And Numerical Analysis Of Seismic Performance Of Drilling With Prestressed Concrete Pipes

Existing research shows that compared with traditional prestressed concrete pipe piles(PHC pipe piles),drilling with prestressed concrete pipes have significant advantages in pile foundation bearing capacity,applicability,degree of construction mechanization,and construction efficiency.Research on seismic performance is still in its infancy.In order to ensure the safety and reliability of the pipe pile while drilling under the action of seismic loads,it is urgent to carry out systematic analysis,testing and experimental evaluation of its seismic performance,so as to ensure the seismic performance of the structure while making full use of its bearing capacity.Based on the above analysis,this paper divides the test conditions into two groups: PHC piles and grouting piles(representing traditional pre-stressed high-strength concrete piles and drilling with prestressed concrete pipes).The seismic performance of drilling with prestressed concrete pipes is systematically analyzed from three aspects: load on the top of the pile,frequency spectrum and amplitude of seismic waves,and connection method of pile and cap.In order to fully reveal the influence of the pile-soil interaction,a nonlinear contact model of the pile-soil contact surface was constructed with the aid of large-scale direct shear test data,and a three-dimensional finite Element model of the pile-soil-structure was further constructed.Through the comparative analysis of the acceleration amplification effect of the pile body,the internal force of the pile body and the pile-soil contact stress,the influence of the grouting reinforcement of the pile end sediment on the seismic performance of the pile while drilling was studied,and the seismic analysis was considered separately.The influence of analysis variables such as different seismic frequency spectrum and amplitude,the quality of the upper load on the pile head and the form of the pile head restraint on the dynamic response of the pile body while drilling.The main conclusions of this paper are as follows:1.Under the strong seismic excitation,the grouting pile has stronger seismic performance than the PHC pipes.Compared with the PHC pipes,the grouting piles can significantly reduce the acceleration dynamic response and the internal force of the pile body at the interface between the upper part of the pile body and the soft and hard soil layers.2.Under the action of earthquake,the acceleration dynamic response of pile body is simultaneously affected by the frequency spectrum and amplitude of ground motion.The plastic deformation energy dissipation of soil and the resonance effect of ground motion and soil are the key factors affecting the dynamic response of the pile body.3.The bending moment and shear force amplitude of pile body are significantly affected by the frequency spectrum and amplitude of ground motion.When the seismic excitation is weak,the internal force of the PHC pipes is smaller than that of the grouting pile;with the enhancement of the seismic excitation,the pile-soil interaction is fully exerted,and the internal force of the PHC pipes is significantly greater than that of the grouted pile.4.Influence of upper load and restraint: Increasing the top load on the pile body makes the pile end restraint effect of the pile and the cap more significant.When the pile end is consolidated,increasing the load on the top of the pile body is equivalent to improving the effect of the pile end fixing,which makes the acceleration response and the internal force of the pile body significantly increase in the connection area between the pile and the cap.When the pile ends are hinged,increasing the pile end load makes the difference of the bending stiffness of the pile cap and the pile larger,which reduces the acceleration response and the internal force of the pile body in the connection area between the pile and the cap.5.The influence of the increase of the upper load on the pile end on the amplitude of the pile-soil contact stress is much smaller than the influence of the difference in soil stiffness at the interface between the soft and hard soil layers on the contact stress of the pile body.