Abstract: The reinforcement cage length in bored piles in several projects was detected by the magnetic logging method and the magnetic logging curves were evaluated. The test results show that the magnetic logging method is an effective and reliable method for detecting the reinforcement cage length in bored piles. For piles with suspected total length and defects, the length of the reinforcement cage is an important factor for evaluating the quality of the bored concrete piles. When the number of longitudinal reinforcement bars change, the amplitude of the magnetic gradient curve-depth is lower in the area with fewer reinforcement bars. When the distance between the surface of the pile shaft and the borehole for magnetic logging is too large, the curve characteristics to be used for determining the bottom of the reinforcement cage and the reinforcement splice locations are becoming not obvious. As a result, the reinforcement bar cage length might not be accurate.

Key words: borehole magnetic logging method, bored piles, length of reinforcement cage, curve characteristics