Development And Research On The Testing Technology Of Two Velocity Measurements

Low-strain reflected wave method is azconvenient,economical and nondestructive pile integrity testing method, which is one of the most popular detection technique of pile integrity. However, the method still has its insoluble limitations that obstruct its further development. On the one hand, it involves the ascertainment of pile length and the position of defect. because of the damping from both the pile itself and the soil around the pile, the energy of excitation vibration, the uncertainty of the velocity stress wave propagating in the pile and other factors, all these make it not easy to judge the length of the pile and the position of defect precisely. One the other hand, as to the pile with existing superstructures, low-strain reflected wave method was found hard to be employeed, complex reflection of stress wave and problem of vibration excitation will be generated by the existing superstructures, which makes it hard to estimate the integrity of the pile. The study of two velocity measurement will improve these problems, but there is not enough research on this measurement domestically.Based on the insufficient of the low-strain reflected wave method, this thesis will systematically studied the problem of the separation of up and down stress wave of two velocity measurement, the excitation vibration method and the development of the apparatus.Firstly, based on two velocity measurement and according to the the propagation rule of stress wave in pile. The functions of the upward and downward wave are successfully divided in principle, and the validity is verified by numerical simulation. And then join the Wuhan Rock Sea Engineering Technology Co., Ltd. in the development of the collection software in apparatus and the analysis software in PC of two velocity measurement,introduction about the collection software in apparatus and the analysis software in PC of two velocity measurement are made next. Then, further field experiment is employed to check and improve the collection software in apparatus and the analysis software in PC. And then, improve the way of vibration pattern through project case. The major jobs are on the influence of the detection signal when transforming the angle of exciting point and the place of the sensors when exciting point is at the top of the pile. When exciting point is at the body of the pile which can be done by cling an exciting block on it, changing the material of exciting block and the exciting hammer, fixing the place of the sensors, finding out the best combination that can get the best detection result. Finally, some project cases are listed which are detected by the instrument of two velocity measurement newly developed.