Abstract: The low strain integrity test has been applied to detect horizontal cracks in concrete piles in recent years. After the preliminary examination by low strain tests, the horizontal cracks in the pile were confirmed by the coring. The factors that could result in the horizontal cracks are investigated based through the investigation of pile location, subsurface conditions, construction technique. The practical pressurized grouting for the horizontal crack mitigations was proposed and implemented and the integrity test on the treated piles could not detect the crack signal indicating a significant improvement of the defected pile. This paper also presents the measures that could reduce the horizontal cracks in the manually dug concrete caissons and the caisson treatment cost could therefore be reduced significantly. 

Key words: Manually Dug Concrete Caissons, Horizontal Cracks in Pile, Low Strain Test Method, Concrete Coring, Pressurized Grouting