Study On The Influence Of Pile Geometric Effect On Vertical Vibration And Its Application In PIT

Pile foundation is an important basic form in China's engineering construction,the scope of application has become more widespread in recent years,and the detection and control of the integrity of the pile foundation has gradually developed into an important issue.At present,the low strain reflected wave method has the advantages of simple basic principle,fast and non-destructive detection,intuitive data interpretation and relatively high accuracy,so it has been used most commonly in pile foundation integrity testing,but the identification of various pile defects is still difficult,and the analysis of some difficult problems is still lacking.In view of this,this paper will mainly discuss the influence of geometrical effects of pile structure on vibration characteristics and its application in low strain reflection wave method,and carried out the following work,achieved corresponding results:(1)The theoretical basis is based on the theory of longitudinal vibration of uneven piles in layered soils under the condition of considering the damping of the pile body material and the general Voigt model of the pile side soil.The analysis and research in the following texts are based on this theory.(2)Using theoretical analysis to study the effect of the size effect of the pile body defect on the response curve in the low strain reflected wave method,mainly discusses the performance of the reflected waveform in the time-history curve under different longitudinal lengths of the pile body defect,and mutual verification by model test and theoretical analysis.(3)Through the comparison of theory and experiment analysis,the influence of the variation effect of pile body impedance on the response curve is studied.It mainly discusses the different reflections of the pile impedance change in the response curve under different gradual forms.(4)Using the combination of theoretical analysis and real pile test,the variation of the size effect of the pile head in the low strain test curve is studied,and analyze the influence of the parameters such as the diameter of the pile head,the height of the pile head and the pulse width on the reflected waveform.(5)Based on the previous research,the effects of length-diameter ratio,pile tip geometry and weld quality on the time-domain velocity response curve are analyzed,and the corresponding laws are summarized.