Study On Damping Effect Of Pile Row On High Speed Railway Subgrade And Foundation Under Earthquake Action

In this thesis,the seismic damping effect of pile row on seismic wave is analyzed through model test and finite element simulation of seismic dynamic response to foundation and subgrade.By changing the variables of pile length,pile diameter,pile burial depth and pile spacing,the following conclusions are drawn:In terms of test:(1)As the pile length becomes longer,the peak acceleration recorded by the sensor gradually decreases,and the area proportion of the damping area gradually increases.When the pile length increases from 0.30 m to 0.50 m,the damping rate increases by 6.6%.(2)With the increase of pile diameter,the peak acceleration recorded by the sensor gradually decreases,and the area proportion of the damping area gradually increases.When the pile diameter increases from 0.05 m to0.15 m,the damping rate increases by 5.7%.(3)When the pile depth increases from0.10 m to 0.30 m,the damping rate decreases by 8.6%,indicating that the change of pile depth has a certain barrier effect on seismic surface waves.In terms of numerical simulation:(1)With the increase of pile length and pile diameter,the peak acceleration and Fourier amplitude of the top surface of the subgrade change little,indicating that the change of pile length has little influence on the seismic performance of the upper subgrade structure.Pile length increased from5.0m to 12.5m,peak acceleration decreased by 1.7%;The pile diameter increased from 0.5m to 1.25 m,and the peak acceleration decreased by 4.9%.The acceleration time history curve of the vertex is similar in each working condition,and the vibration frequency and period of the vertex of the subgrade are similar with the increase of pile length and pile diameter.(2)Compared with the pileless condition,the peak acceleration and Fourier amplitude of each measuring point at the roadbed slope will decrease somewhat,and the peak value will decrease with the increase of pile length and pile diameter.The increase of pile length and pile diameter is beneficial to the stability of roadbed slope.(3)Pile spacing and pile buried depth have obvious effects on the acceleration peak and Fourier amplitude of the upper subgrade structure.When the pile spacing or pile buried depth is set to be large,the curve peak value will be close to the curve peak value in the pileless condition,and the shock absorption performance of the upper subgrade structure will be poor.When the pile spacing increases from 1.5m to3.0m,the peak acceleration increases by 15.4%.The pile depth increased from 1.0m to 4.0m,and the peak acceleration increased by 9.3%.(4)When piles are buried in the foundation,the peak acceleration of pile body will gradually decrease along the pile body,and the force of pile group is more uniform.The acceleration peak value is the largest at the top of the pile,the second in the middle of the pile,and the smallest at the bottom of the pile.