Research And Application About Integrity Detection Of Large-diameter Bored Pile In Bridge Engineering

Large-diameter bored pile has been widely used in the bridge engineering. There are several types of detection methods. However, it is still a difficult problem for the engineers how to choose appropriate methods. So that it can not only guarantee the safe service of the pile foundation but also reduce the cost.Cross-hole sonic logging has many advantages, such as detecting carefully, abundant information, accurate and reliable results, unlimited by the length of pile. It has been becoming the important means for the integrity detection of bored pile, especially for large-diameter bored pile. The principle of cross-hole sonic logging measuring concrete integrity is presented. And the foundation pile integrity detection of the Chongyang Bridge with cross-hole sonic logging is introduced. The number of access tubes which is needed for cross-hole sonic logging and the criterion for pile integrity evaluation are discussed. Several conclusions can be drawn from this study. First, the number of access tubes increases with the pile diameter. But, four access tubes are absolutely enough for the ultrasonic wave generally covering the whole body section of pile. Second, It is more scientific than others that the criterion of pile integrity evaluation for cross-hole sonic logging given by the《Technical Code for Testing of Building Foundation Piles》(JGJ 106—2003), but there are also some defects. Third, the pile defects'nature, size and space position should be synthetically judged by records of construction and geological condition in addition to velocity of sound, amplitude, PSD and some other criterions.At the same time, cross-hole sonic logging, low strain wave-reflecting method and drilling core method are summarized. Then, methods of integrity detection for large-diameter bored pile in bridge engineering have been discussed. It offers technical support for pile detection and construction of the Chongyang Bridge.