Critical depth of displacement piles in overconsolidated cohesionless soils

(Despite ample research reported on the shaft resistance of closed-end displacement piles, the mechanism of the shaft resistance in cohesionless soils is not fully understood. In the literature, the available theories produce a wide range of discrepancies in predicting the shaft resistance of these piles. This is due to the complexity of incorporating the stress history and recognizing the critical depth. The role of the overconsolidation and the critical depth concept has been the subject of debate for some time. Arguments were made for both sides, nevertheless, no definite conclusion has yet been drawn. This paper presents experimental investigations on the capacity of closed-end displacement piles in overconsolidated cohesionless soils. The set-up was capable of measuring the overconsolidation ratio of the sand, and the shaft resistance of the pile shaft. It is of interest to know that the critical depth was observed only when mean shaft re)sistance was analyzed.