Theoretical and experimental research on multi-point dynamic testing method for pile bearing capacity
Compared with static load test(SLT),high-strain dynamic test(HSDT)of pile foundation is more effective,rapid and less costly.A new HSDT method was proposed and verified,which is called the multi-point dynamic method(MPDM).The difference and influence factors of pile capacity curves between SLT and DLT were studied through theoretical analysis and model experiments in the presented paper.Based on the nonlinear soil resistance model,the dynamic discrete spring-mass model of single pile under high strain condition was established firstly;the analytical expression of impact force of free-fall hammer was derived and the discrete difference solution was given.The dynamic load curves under different pile lengths was calculated based on MPDM and compared with SLT results and results predicted by Statnamic method.On this basis,model experiments were conducted to explore the difference of dynamic and static capacity curves,and to verify the reliability of MPDM.The results have shown that the capacity curve predicted by MPDM was accurate for pile of short length;the prediction results was better than that of Statnamic method for long piles.The difference between the dynamic and static curves was related to the wave effect of pile,and the prediction accuracy of the multi-point dynamic measurement method can be improved by adjusting the excitation conditions at the pile top to attenuate the wave effect.The presented theoretical model,which can consider the soil nonlinearity,accurately predicted the dynamic response of model pile.And it is applicable for low stain and high strain dynamic load conditions.This research is helpful to study HSDT methods,dynamic theoretical model and the difference between dynamic and static capacity curves.
pile foundationspile foundation bearing capacityhigh-strain dynamic testmulti-point dynamic methoddynamic and static comparison
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