Behavior of long PHC piles driven in Shanghai soft clay

The prestressed high strength concrete pipe(PHC) piles of 64～77 m are driven into Shanghai soft clay. The bearing capacity of open-end piles are affected by the degree of soil plugging. There are no reports about the effect of soil plugging and bearing capacity of long slender pile. Based on the results of field tests, the records of driven piles and the results of static load tests with the PHC piles are presented. The records of driven pile show that the blow counts per meter and the length of soil plug vary with the depth of piles in ground. Especially, when piles are driven into fine sandy artesian aquifer, the length of soil plug increases rapidly with the depth of piles driven in ground. A month later after the completion of pile installation, some soil plugs are destroyed under high artesian head. According to the SPT tests in soil plugs, the influence of artesian aquifer on the stability of soil plug is discussed. The vertical load tests are performed posteriorly to the SPT tests of soil plugs. Furthermore, the effect of the soil plug is discussed with respect to their contribution to the bearing capacity of long PHC piles.