Theoretical Study And Application On Dynamic Testing Of Large Rectangular Cross-section Pile

Pile foundation is used as an effective form of basic and widely used in engineeringpractice. Due to the large pile of rectangular section there is a big difference comparedto the circular cross-section pile, stress wave propagation in the large rectangular cross-section pile has its own characteristics. In this paper, a three-dimensional pile-soilmodel is established, three-dimensional elastic wave equation is differenced and theHigdon artificial absorbing boundary is introduced on the computational modelinterface, definite solution of the three-dimensional elastic wave equation are calculatedunder transient vertical excitation force.By calculating program that designed by MATLBA language, stress wavepropagation characteristics of large rectangular cross-section pile are got in the three-dimensional pile-soil system. Due to the impact of the pile and the pile-soil interfacecorners, the disruptions of stress wave propagate in rectangular cross-section piles aremore than circular cross-section piles, in order to minimize wave field interference, thebest pick-up range in the low strain testing is proposed at square and rectangular cross-section piles. The influence of force parameters on the dynamic excitation testing, thenumerical simulation characteristics of dynamic excitation testing on various defectivepiles and expanded diameter piles are analysed, and it are focused on the analysis of theasymmetric defects in dynamic pile testing process, numerical simulation of theresponse of different depth defects reflected the changes of the defect. The defectreflections of numerical simulation response with different defect depth are analysed inthe dynamic testing of the asymmetric defective piles.In order to improve the efficiency of low strain numerical simulation of pile, basedon the traditional difference method, the variable step staggered finite difference methodis introduced into a three-dimensional numerical pile-soil model. Since the method itselfcan change difference grid, the calculation process are more flexible and easy tocalculate, and the memory requirements and the computation time are reduced whileensuring accuracy. It has achieved good effects.The engineering piles were simulated and calculated, and the numerical calculationresults were compared with the measured curves to verify the correctness of thetheoretical results.