Study On The Impact Of On-site Operation On The Results Of Dynamic Testing Of Pile

At present, low strain reflected wave testing is the most widely used method for non-destructive assessment of pile defects in engineering practice. The defects in pile and length of pile can be tested by this method. Low strain reflected wave testing has complete theoretical foundation and advanced diagnosis technology. However, there’s a lack of research about the practice of low strain reflected wave testing and a lot of problems remaining to solve. This paper investigates the influences of some operations in low strain test. The principal contents and detailed work are follows:1. The adhesive bonding effect is simulated using the model of Voigt, a new dynamic model of two-degree of freedom system is established. An admittance function relating the displacement of the accelerometer oscillator and base is analytically derived in Laplace transform space. Then, with the use of the already known velocity-response function at the top of pile, the convolution theorem and the inverse Fourier transform, a semi-analytical solution for the output of the accelerometer subjected to a semi-sine wave exciting force has been derived. At last, the solutions obtained are used to analyze the influences of stiffness and damping of accelerometer adhesive.2. Based on the dynamic model established before, the influences of external force acting on the accelerometer base are investigated. The semi-analytical solution for the output of the accelerometer under the action of external force is derived. With this solution, we discuss the influences of external force exerted by testing personnel to the velocity-response curve of low strain test.3. An adjusted dynamic model is established by changing the mass of accelerometer base to simulate the behavior of transforming the accelerometer by testing personnel. And the gravity of the mass added to the accelerometer base is considered. With the use of the convolution theorem and the inverse Fourier transform, the semi-analytical solution for the output of the accelerometer is derived. With this solution, we discuss the influences of accelerometer transformation to the velocity-response curve of low strain test.4. With the use of ABAQUS finite element analysis software, a tubular system is established. The velocity-response curves are got with accelerometer installing at different location of the pile top. By setting different defects in different length of pile, the paper analyzed the influence of arrangement of accelerometer to the result of low strain test of pipe pile.The analysis results of this paper can serve as a supplementation of the pile foundation vibration theory. And it’s also a good start of practice research of low strain reflected wave testing. Based on the results of this paper, a normalize use of low strain reflected wave testing can be spread in actual project.