Experimental study on shaking table model of six piles with large diameter and variable section in different thickened soil layers

In order to study the dynamic response characteristics of six-pile foundation with large diameter and variable section in different layers of liquefied soil， 5010 waves with ground motion intensity of 0.15g， 0.25g， 0.35g and 0.45g are selected through in door shaking table model test based on the solid project of Xiangan Bridge in Xiamen Second East Passage. The dynamic character istics of saturated sand pore pressure ratio， pile acceleration， pile bending moment and pile top horizontal displacement of six pile foundations with large diameter and variable section are studied when the thicknesses of the liquefied soil layer are 30， 40 and 50 cm. The results show that the acceleration and bending moment of six-pile foundation with large diameter and variable section change abruptly at the interface between variable section and soil layer under different thicknesses of saturated sand layer. Under the same soil thickness， with an increase of ground motion intensity from 0.15g to 0.45g， the pore pressure ratio of saturated sand， pile acceleration， horizontal displacement of pile top and pile bending moment all increase. Under the ground motion intensity of 0.15g， the stable value of pore pressure ratio of the six-pile foundation decreases with an increase of saturated sand layer thickness， but the horizontal displacement of pile top， pile acceleration and peak bending moment of the six-pile foundation gradually increase and in crease. It is suggested that in the design of large diameter variable section pile foundation in liquefaction site， special consideration should be given to the dynamic response difference of six large diameter variable section pile foundation under different thickness of liquefied soil layer， and pay attention to the flexural performance of the interface between the variable section and soil layer， so as to ensure the seismic performance of the six pile foundation.