Bleeding and channelling in bored piles

Bleeding is known to occur in bored piles. The generally accepted view is that bleeding in piles is confined to the upper part of the pile only. Extensive integrity tests consisting of 244 sonic logging tests and 80 dynamic load tests on bore piles as well as continuous corings from top to bottom of the piles revealed that some 28 bored piles were found to have channelling of concrete at various depths. Most of them were larger diameter piles. This paper attempts to propose a theory for the bleeding and channelling of concrete to explain the mechanics of the occurrence of channelling in bored piles. The theory is verified by the close correlation of the predictions of the theory with field observations of the integrity tests. Based on the proposed theory, recommendation with regards to the quality of concrete will be made to avoid the occurrence of channelling of concrete in large diameter bored piles.