Research On Static-Dynamic Mechanical Behaviors Of Pier Pile Under Vertical Load

In recent years, with the rapid development of economy in our country, piles have widely been used in the construction of the piers and high buildings and bridges widespreadly which proceeded toward the multiple pile and large diameter and super length. While the design theory of the pile gained progress rapidly such as composite foundation, theory of loosening pile, pile dynamics, nodestructive test of the pile foundation. Considering the variation of the soil and complicated coupling of the pile and soil, much more are required in the theory of the pile foundation.In the coastland of the pier, the top sediment is quaternary deposit which the thickness varied from the meters to the dozens meters. The weak soil such as fill and mud silting are presented between them, the characteristics of the engineering geology is complicated. As a result, the mechanical behavior of the pile is also complicated. Considering the pier constructions, long free parts existed in the top of the ocean floor. In the combination of the vertical static and dynamic load, the bearing behavior is much more complicated and the stability of the pile was losed easily. So, the study on the coupling of the pile and soil and vertical bearing and the bulcking behavior is help for understanding the coupling relationship of the pile and soil and gaining the rules ot the pile static and dynamic buckling.In this dissertation, based on the the pile theory and static and dynamic research in our country and abroad, the study are detailed in the following:(1) Based on the high pile pier of a habor, the static load test and large strain dynamic test and strain survey were carried out. According to the results, surrounding and end load transformation of the pile were gained, regularities of distribution of hammering maximal force, maximal transferring energy and maximal compression stess were obtained. Comparing the results of the static test and large strain dynamic test, the coupling behavior of the pile in the process of the drain can be achieved with the pile and soil model and parameters.(2) Considering the contact effect between the pile and soil, load transformation of the pile and soil was analyzed with finit element method as well as the pile and soil material and pile geometry influencing on the vertical load bearing of the pile. Many parameters influencing on the load-settlment curves were presented such as pile length, pile radius, moduls of the pile material, the modulus ratio of the pile and soil, the poisson's ratio. The relationship between axial force and pile length was analyzed as well as the pile radius and the modulus of the pile material and soil seam compress modulus at the end of the pile. The rules of the load transformation were gained. It was supposed that the pile length and the ratio of the length and radius should be optimized and the elastic modulus of the pile should be increased appropriately. The bearing capacity of the long length pile should be controlled on the deformation. The posson ratio of the pile material has minor affected the load settlement curves. According to the analysis of the surrounding and end force of the pile, it was shown that the surrounding force and end resistant force was asynchronously and influenced muturely and the behavior was related with the soil material and the length below the earth surface.(3) The static buckling model was constructed with the WINKLER mechanical model. The parameters influencing on the buckling behavior of the pilw were analyzed with the ANSYS program such as the stiffness of the surrounding soil, the length below the earth surface, the obliquity of the pile etc. The changing rules of the critical load of the pier pile static stability were presented. It was shown that the buckling critical load of the pile were mainly related with the resistant force surrongding the pile, the geometry and scale of the pile section, obliquity of the pile, resistant force model and the top soil seal stiffness. The friction force of the pile influencing was minor which can be neglected in most cases. The weight of the pile influencing should be considered according to the pratical construction.(4) The dynamic model was constructed according to the Smith pile-soil coupling mechanical model. The response of the pile subjected to the drain load was analyzed. The time displacement and velocity curves of the pile top and end point were presented in the case of the different pile radius and length below the earth surface. The displacement and velocity and axial force distribution along the pile were analyzed when the maximum displacement and velocity appeared. Based on the analysis of the parameters influencing on the dynamic response of the pile such as drain load, length below the earth surface and pile length, it was shown that drain load and pile radius and free part length were the primary factors influencing on the lateal displacement of the pile. While the length below the earth surface of the pile influencing on the lateral displacement was minor.(5) The energy transfer between the pile and hammer was analyzed with survey curve fitting method of the dynamic test. With statistical analysis of the energy transforing from the top to the end of 132 piles, it was shown that the efficiency of the pile and hammer system was concordant with the theory analysis results. The maximum compressive stress was mainly located at the middle of the pile in the process of the pile sinking which proved the computation results. Combing the field test, the modification of the pile-soil model in the measured curve fitting method.