Research On Ultrasonic Transmission Method To Detecting Cast-in-place Pile Quality

Pile foundation is a kind of embedded engineering, which is usually located below the ground surface and water level. These projects are easy to have some quality problems because of the complicated construction procedure, high technical requirements and great construction difficulty.Based on the pile foundation testing in the Changzhou Viaduct project, the quality of concrete bored piles is studied. Firstly, from the basic principle of the UTM (ultrasonic transmission method), the statistics of the wave velocity and amplitude in the case of different pipe-distance are made to obtain the variation law. Then, the relation curves of "pipe-distance vs. wave velocity" and "pipe-distance vs. amplitude" are got by fitting methods.On the other hand, series of strength testing and ultrasonic velocity testing are made to concrete blocks at different levels. These blocks are made of commercial concrete and have experienced at least 28 day's maintenance. The adjusted f-v curve and the regression equation are established, and the reliability of the pile body strength is calculated as well.Then, the evaluation method of the quality of concrete bored piles through UTM is studied. Comprehensive judgment method in fuzzy mathematics is applied to the evaluating system to compare the existent criterion in the related codes. The parameters such as the wave velocity, wave amplitude and wave shape in the result of ultrasonic testing can be comprehensively evaluated by the fuzzy mathematics methods. As for the integral estimation of the pile body quality, multilevel fuzzy comprehensive judgment method is used. Through this method, a reasonable judgment of the pile quality can be derived from testing results of different methods including ultrasonic transmission method, high-strain dynamic testing method, low-strain dynamic testing method and block strength testing. In this thesis, a fuzzy comprehensive judgment is made to a particular pile tested in site through specific analysis and calculation.Finally, the research achievements of UTM are applied to the engineering practice. This thesis gives some examples of the common problems in UTM testing such as the correction of the pipe inclining, the evaluation and processing of the defect piles. All of these applications in practice prove the usability of the achievement in this thesis.