Driven cast-in-situ piles in granular soil: applicability of CPT methods for pile capacity.

Most CPT-based design methods for driven piles are heavily influenced by research on preformed driven piles. In this paper, a critical review is made of the ability of these methods to predict the total capacity of driven cast-in-situ (DCIS) piles. To this end, a DCIS database of 16 piles (with adjacent CPT profiles) is developed which incorporates new DCIS load-test data from UK sites. Initially, instrumented piles from the database are used to illustrate that DCIS and preformed piles have comparable shaft and base resistance characteristics. The database is then used to study of the performance of three simplified and four advanced CPT-based displacement pile design methods in estimating the total capacity of DCIS piles. Statistical analyses show that in general, the advanced CPT methods provide the best estimates of DCIS total capacity, although capacities tend to be under predicted by most methods. This tendency may be attributed to enhanced interface friction between the cast-in-situ concrete and the soil compared to that developed with preformed piles.