The Factors Influencing The Integrity Detection Results Of Pile Foundation Based On The Low-Strain Reflected Wave Method And Countermeasures

With the rapid development of infrastructure, pile foundation has been used in a wide range of construction cosmically. But the quality of the pile foundation caused more and more project problems, therefore it is important to detect the pile quality by effective means and to avoid engineering accidents. The low-strain reflected wave method is most popular way to test the pile integrity in our country presently, because the method is light, fast, economic and other advantages. However, because of the theoretical lack and problem complexity in measurement of pile foundation, the method is influenced by many factors. Only we who understand the factors details influencing the test results could propose the corresponding countermeasures.This paper first introduces theoretical basis of the low-strain reflected wave method, one-dimensional wave theory, then analyses the technology and method of the low-strain reflected wave method, and the factors influencing the test results and proposes the corresponding countermeasures along to the processes of the test. Last, based on ANSYS finite element analysis software establishes a three-dimensional model to simulate some factors influencing the waveform and prove the accuracy of the countermeasures. First, simulates the speed waveform of the complete pile and proves the authenticity of ANSYS simulation according to theoretical analysis. Second, simulates the speed waveform when changes the test position that the sensor installed and proves that sensor should be put near two thirds of the radius of a pile. Third, simulates the speed waveform when changes the loading area and size and proves that increase the loading area and size at the appropriate size can receive a better test results. Fourth, simulates the speed waveform when changes the type of hammer and proves that some time change the type of hammer can receive a better test results. Fifth, simulates the speed waveform of the defective pile like expanding, shrinking, isolation, breaking. Summarizes the characteristics of the defective pile's waveform and the points of analysis. Compares the speed waveform of the defective pile foundation between the pile that surrounded by soil or not. Last, simulates the speed waveform of the isolation pile after filtrating.The results of the paper will have some guidance to the integrity testing of pile foundation.