Research On Damage Detection And Supporting Capacity Evaluation Of The Pile By Dynamic Characteristic

With the rapid development of transportation in our country , the bridge construction quantity are getting more and more , the pile foundation is also widely used in the bridge construction. Therefore, the pile foundation quality detection has become a key in the bridge construction .The pile foundation supporting capacity and the integrity detection are two important contents in the pile foundation quality, its detection method mainly are the traditional static testing and the rapidly development of dynamic testing in recent years. Because the dynamic testing simply and time-saving, thus the dynamic testing has became the most prospect method in the pile foundation quality detection at present.The longitudinal vibration theory of pile is the basis of many kind of method in dynamic pile testing, development the pile longitudinal vibration theory which can be used to explain the dynamic response between pile and soil,the mechanics of pile testing and to illustrate the pile testing curves.Based on longitudinal vibration theory of the pile in this paper, the pile damage and supporting capacity has been detected and evaluated from the method which are theoretical analysis, model experiment and scene test unify, the primary coverage includes:(1) Based on the one-dimension stress wave theory, the inherence vibration of the rod in the both fixed,an end fixed and others freedom and the both end freedom, as well as the forced vibration of the rod and longitudinal vibration of the pile has been analyzed, then the response of the pile-soil system in longitudinal vibration has been gained. has discussed reflection situation of stress wave in the pile of the fixed end, the free end and the variable cross-section.(2) The soil-pile vibration model of the defective piles has been established., and the analytical expression of the impedance function at the top of the pile in arbitrary cross-section get from the Laplace transform and impedance function, further, the speed conductance and the speed time-domain response has been obtained, as well as the dynamic testing pile transient response of the attenuation characteristics, the multi-frequency vibration characteristics, the spatial characteristics and the frequency spectrum characteristics has been analyzed.(3) Take the pile continual member as a model, the basic theory of the curve fitting,constitutive model of the concrete pile shaft and piles -soil coupling model of the static and the dynamic has been introduced; According to the stress wave theory, the time-domain analysis and frequency-domain analysis of the reflected wave method in detection defective of pile and how to detection the pile length and the defective position has been introduced.(4) The influence of the defective position for the reflected wave signal studied from the analog computation based on stress wave theory, as well as The weaken characteristic of the stress wave along the pile shaft in the different pulse width and material damping has been confirmed from the model pile experiment.(5) The pile continual member model has been established based on curve fitting method ,the pile foundation supporting capacity has been inversed from the genetic algorithm by the high strain, and contrast with the static load experiment, has confirmed the genetic algorithm feasibility.